Weighted Companion Cube Cake

This was a trimph./ I’m making a note here, ‘huge success.’/ It’s hard to overstate my satsifaction!


After hours and hours of sweating over a hot stove, the companion cube cake (technically a giant brownie) has been completed!

Final ingredient tally:

  • 7 boxes brownie mix
  • 4 cups vegetable oil
  • 22 eggs
  • 3 and half giant cans white frosting
  • some jello mix
  • 5 chocolate chip cookies

So it’s some serious cake. The dimensions are 18 x 18 x 18 centimeters, excluding the giant corner pieces. If you want to follow the construction saga, read on!

I was trying to come up with something to do for my gf‘s birthday, which was yesterday. We try to do things for each other that aren’t too costly (we’re poor college students) and that we can both appreciate. This often includes video games, making crazy desserts and other food items, etc. Since I had just finished playing through Portal in a failed attempt to knock down all the cameras in the game, I had the Companion Cube in mind. So, I decided to make my gf a weighted companion cube birthday cake!

I googled “companion cube cake” to find out if and how this had been done, and got back insufficient results. So I decided to make the most kick-ass companion cube possible. Out of brownies.

Part 1: Making the basic cube

I got an 8″ x 8″ square pyrex baking dish to make the base cube, and bought my first bunch of ingredients.

first batch of ingredients

I figured four boxes of brownie mix would do it, since it seemed like I could make a cube with that quantity. I didn’t have any other plan at this point, except that I knew I needed icing and something to make that icing gray (jello). I also knew that I needed good structural support, so I made the brownies fudgy (instead of cakey)

So I started baking. And stacking. And baking. I chilled each new brownie pan in the fridge until I could handle it and put icing on it without it melting all over, and glued them together (with icing) as they came out. If I’d had more pans, this process would have been much faster…

After the first two were stacked I realized that the gentle sloping of the pan was going to be a problem. I needed fairly straight edges. So after the third one was done and placed, I cut the edges down to make them much more square.

After the fourth one was stacked I had a thought along the lines of “Holy crap, this thing still isn’t tall enough to be cubic… I’m going to need more brownie mix!” After the trimming of the edges, it had become 18cm on a side, but was still only ~ 11cm tall. Implying I would need 6 damn brownie batches just to make the base cube. After purchasing three more boxes, I decided to make this next one in cake mode, hoping that it would be tall enough to get me to 18cm high without having to add a 6th layer.

Thankfully, this put me at about 19 cm tall. But, the cake mode ended up giving me a hugely rounded top. So I tried placing it upside down first (hence the icing on the peak in the above image) and then realized that the gaps would be too huge and the thing would be too tall. So I decided to flip it the other way and trip the dome off the top until it was the right height.

This worked pretty well, but I still had those low corners to deal with. To square them off I covered them in icing and use shards of brownie from the edge-trimming process as space-fillers.

The basic cube was complete! It was late and I didn’t want to bake anymore (this was Friday night), so I wrapped the thing in seran wrap and went to bed.

Part 2: From brownie cube to Companion Cube

I got up the following morning (yesterday) and started baking again. I had two things of brownie mix left for all of the other components, which didn’t seem to be enough. The corner parts didn’t need to be that thick, so I made the next batch in a 9″ x 13″ pyrex dish. Also in brownie mode.

I wasn’t actually sure how to go about making the corner pieces, since they would need to fit together in puzzle fashion and would have to be identical on each side. I looked up the companion cube papercraft that I had found earlier, downloaded the jpeg and took pixel measurements with Paint.net (the best Paint replacement that exists). The basic cube in the image was 489px, so I divided my cake width by this to get a scaling constant of 18cm/489px= .03068cm/px. This way I could take measurements on the papercraft image in pixels and convert them to the centimeter scale of my cake. After fiddling with this I realized it was going to be a huge pain to measure and cut out all of these pieces, so I printed off some templates instead.

For anyone interested, I did this by cutting out the part of the image I was interested in (the heart and the corner pieces) with Paint.net and then scaling them to the size I predicted them to be. I printed them on regular paper, cut them out, and cut around them on the brownie slab.

This way I didn’t have to deal with circle edges either; I could just cut around the form. To make the corner pieces in 3d I needed three different shapes. I needed one with no overlap, one with one side overlap, and one with two sides overlapping. This way they would be glued together, and to the corner of the cake, in a stable fashion. This is confusing so I’ve edited a picture to show what I mean:

The overlapping parts hang off the face of the cake that the specific corner piece is stuck to, and then connects with the edge of a corner piece on an adjacent face. For the top for corners I needed four of each type. For the bottom, I just needed the no- and single-overlap pieces, since the cake is way too heavy to be supported with bottom pieces.

The first large brownie pan gave me enough to make the first three corners. I had trimmed without the hard edge parts for those, but new that if I was going to pull off not having to buy an 8th brownie mix, I would have to use edges on the next one. I popped the 7th (and last) batch into the oven, and then kept editing the cake while I waited.

I had decided to use cookies for the circles in the middle of each face, and bought a package so that they’d all be fairly round and about the same size. A this point I felt that everything was going to go fine, except the icing. Fortunately the gf has some skills in this area and swooped in to help. She mixed up three batches of colored icing, using blue, red, and green jello powder for coloring. We ended up with an off-white, a medium-gray, and a light pink for the various parts of the cube. She used the heart cutouts I had printed to craftily paint hearts onto the five cookies (one for each face but the bottom), which would be added at the end.

In the game, the companion cube has no sharp corners on the outside pieces, so I carefully cut the corners of each piece. It went fairly successfully, though I learned that, for the rest of the corners, it makes more sense to trim them before they go on the cake.

When the last pan had come out of the oven and cooled, I managed to use every square inch of the thing to get the remaining pieces. I trimmed them down and iced them to the cake. We added icing to some of the corners to make sure the contrast was strong enough.

It seemed to be, I began filling in the faces with the darker gray icing. There were still fairly large gaps between the layers, but we had plenty of icing so I did a lot of mortar-work while covering the surface.

I then iced the corners with the lighter icing, and had the gf add the little strips of light gray between the corner pieces as well as the lines of pink. The Companion Cube cake was completed!

To please GLaDOS, we then threw the cake into the AI incinerator…

… and didn’t incinerate it. That would have been a very sad end to such a huge project.

And finally we were prepared to eat!

And even with the help of a couple friends, we didn’t get very far…

So, to my gf, happy birthday!

To see all of the pictures, and at any size you please, check out the flickr set.

55 thoughts on “Weighted Companion Cube Cake

  1. Congratulations! If you can both devise and construct such a confection, there’s nothing you can’t do in life.

  2. you put incredible effort into this. if i didnt give up after all the brownie stacking i would have when i remembered the corners. nice work man

  3. Although it looks like you went through a big deal for this giant brownie, it looks like after eating one bite I would need a huge glass of milk. >.<

  4. You should have made it out of:

    1x 18.25 ounce package chocolate cake mix
    1x can prepared coconut pecan frosting
    3/4 cup vegetable oil.
    4x large eggs
    1x semi-sweet chocolate chips
    3/4 cups butter or margarine
    1 2/3 cups granulated sugar
    2 cups all purpose flour

    Fish shaped crackers.
    Fish shaped candies.
    Fish shaped solid waste.
    Fish shaped dirt.
    Fish shaped ethyl benzene.
    Pull and peel licorice.
    Fish shaped volatile organic compounds and sediment shaped sediment.
    Candy coated peanut butter pieces.
    Shaped like fish.
    1 cup lemon juice.
    Alpha resins.
    Unsaturated polyester resins.
    Fiberglass surface resins.
    Volatile malted milk impoundments.
    9 large egg yolks.
    12 medium geosynthetic membranes.
    1 cup granulated sugar.
    An entry called ‘how to kill someone with your bare hands.’
    2 cups rhubarb, sliced.
    2/3 cups granulated rhubarb.
    1 tablespoon all-purpose rhubarb.
    1 teaspoon grated orange rhubarb.
    3 tablespoons rhubarb, on fire.
    1 large rhubarb.
    1 cross borehole electro-magnetic imaging rhubarb.
    1 tablespoons rhubarb juice.
    Adjustable aluminum head positioner.
    Slaughter electric needle injector.
    Cordless electric needle injector.
    Injector needle driver. Injector needle gun.
    Cranial caps.
    Deep penetration agents.
    Gas and odor control chemicals.


  6. You are amazing! I wish my boyfriend would make me a Weighted Companion Cube cake. It’s my birthday this Sunday and I wanted to make a cake like that. Thanks for putting this on here, I may use when I’m making my own cake. Once again, YOU ARE AMAZING!

  7. You’re ugly.

    Just kidding, but it was nice of you to leave such an uplifting comment on something I spent hours creating.

    You’re very rude. Enjoy you’re spaghetti.

  8. I really just wanna eat it! It looks so nice!! Must’ve taken ages to get the shape right! Well done! :)

  9. You so TOTALLY rock!

    Your gf must lub you to death over all of this…
    I wonder tho How long did it take you TO eat that?

    1. Thanks for the wonderfully written critique of my work! I was under the embarrassing belief that my cube cake wasn’t that bad, though it could have used a little bit of improvement, but thankfully you have shown me the errors of my thinking through your impressive intellectual prowess.

  10. So considering this is a freakin’ huge cake, would halving recipe still work with the design of it?

    1. yeah, but you’d have to scale the other stuff a little differently. I based the size on the pan I was using to make the brownies, after I cut the edges off. I measured the square size of the first one and the height of the brownie, then figured out how many I’d need stacked up to get a cube. Then I scaled the cutouts for the side pieces accordingly, using the paper-cube sizes. Definitely doable though.

  11. Good thing it is a brownie and not a cake, otherwise we would have known you lied.

  12. oops, sorry about the mints part, I’s talking to my sister. Trying to steal my profile on Halo 3. But mints are good, remember this for when I return… WITH MINTS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

  13. is it like not awesome or something to put more than one comment in a single strand of comments in a line in which each of your comments follow one another/eat mints?

  14. This is a beautifully constructed cake. Its appeals to the gamer and cake lover inside of me. The cake wasnt a lie :)

    It would be awesome if you can make more cake/game crossovers. Something like, Master Chiefs Helmet, A Mario Mushroom/star or even the fable series Hero’s Guild Crest :).

    Keep up the good work, its appreciated and respected.


  15. it would’ve helped if you’d also cut the bulge off the top. thats what proffessional cake makers do

  16. man if that cake was possible then please don’t attempt to divide by zero

  17. Thanks mate, like you. Been searching about the internet for how to make my girlfriend such a cake for her birthday. I think I’ll do it the way you did! And get to save some effort courtesy of your already having done it and you were able to find out what you needed entirely beforehand. =]

    Thanks in advance!

  18. Man, you are genius. I’ve been searching for a good example to base the companion cube cake I’m making for my boyfriend for his birthday for a long time. I’ve deemed yours the best.
    It is incredibly huge, I must say. I’m going to make my cake out of german chocolate cake so it’s not as dense and a little taller so there’s less layers involved. I’ll also make it 5 inches by 5 inches after seeing how much was left over from you guys! Bet your gf was very happy though!

    1. Fyi. Brownies are better to work with, despite having to use more layers… Cake falls apart if it’s not rock solid while trying to sculpt it. :|

  19. Try doing a crumb coat first next time, and you won’t have all those little bits scarring the cake! Nice job, just looks a bit messy with all the chocolate bits in the frosting.

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