Rainbow Cake via Whisk Kid
White Cake (but not really)
2 sticks (226 g) butter, room temp
Preheat the oven to 350F degrees. Oil and line how ever many 9” cake pans you have (I have three and I just reused them).
Sift together the flour, baking powder and salt. Set aside.
Cream the sugar and butter, then add the egg whites (I cracked them all into one bowl) and add them a little at a time. Add the vanilla and mix until fully incorporated. Then, alternating between wet and dry, add the milk and flour mixture in two parts.
Divide the batter amongst 6 bowls (I did it by weight. Weigh your mixing bowl before you begin adding ingredients and then subtract the weight of the bowl from the final measurement after the batter is completed. Divide that number by six and add that weight of batter to each bowl), and then whisk a fair amount of the appropriate food color into each bowl. Keep in mind that the color of the unbaked batter will be the color of the baked batter. Pour into the pans and bake for 15 minutes each.
When you remove them from the oven, let them rest on the cooling rack, in the pan, for ten minutes. Then flip, cover, and stash them in the fridge to cool quickly.
Lemony Swiss Meringue Buttercream
To fill and crumb coat:
Cook the egg whites and sugar in a small saucepan over medium heat, whisking constantly, until the sugar is completely dissolved (test by rubbing some between your fingers. If it's completely smooth, it's done). Pour into another bowl (a stand mixer is preferable) and whip on high speed until room temp. Then, on a medium-slow speed, add the butter, waiting until each piece is completely incorporated before adding the next. After all the butter has been added, turn the mixer back to high speed and whip until it has come together, about five minutes. Add the extract, beat briefly and then use.
If the buttercream seems soupy after all of the butter is added and does not come together after whipping, refrigerate for 5 to 7 minutes and continue whipping until it becomes fluffy and workable.
Sweetapolita's Notes & Kid's Doodle Cake How-To:
1. For tips & tricks on making Swiss Meringue Buttercream, both Kaitlin & I have posts about this, so lots of info!
2. You may find my previous post 50 Tips for Baking Better Cakes helpful with this cake (and hopefully others).
3. I was worried at first that I somehow made the layers too thin, but they were perfect, so don't panic when they seem almost pancake-like! Once you pile 6 of those layers and all of that buttercream, the cake is a perfect height. Mine was about 4.5" high. Use a 9-inch, 1/4" thick cake board when building the cake.
4. To make the doodle cake, cover the buttercream cake in white fondant and refrigerate overnight. Remove cake from refrigerator and let child (or anyone!) colour all over cake using Gourmet Writer Food Decorator Pens. Place cake back in refrigerator every 15 minutes or so, if it begins to soften before child is finished (otherwise you will get dents in the cake). It's also fun to have everyone at a birthday party sign the cake, write a message, draw a picture, etc!
5. You can store finished cake in refrigerator, but serve at room temperature or buttercream won't be soft enough and the flavours won't come through as intended. I typically take this type of fondant-covered cake out of refrigerator about 6 hours before serving. Just a note the cake will dent very easily when ready to serve, so avoid touching the cake itself.