This pattern is basically the cube-shaped version of white Chiffon Cake, with the major difference being that this cozy will show the “inside” of the cake with some cake layers and frosting.
I chose Red Heart Soft for the chocolate because I think it’s a really nice, rich color. I generally prefer working with Vanna’s Choice, since I like the feel of it personally, but you really can’t beat the color here of the Red Heart Soft. I chose Deborah Norville Everyday Soft Worsted for the yellow, because it is really bright, saturated, and kind of a cartoony version of what I imagine yellow cake to be. But you can pick your favorite cake flavor and frosting flavor to work up this cozy. (You can click on photos to enlarge them.)