Rainbow Ice Cream Cake

For my daughter’s birthday, she asked me to make her a rainbow cake. This gave me pause because most of the rainbow cakes you see on Pinterest are made with artificial food coloring, but I try to avoid that whenever possible. The natural colorings made from fruit or vegetable purees, come out pastel at best. Things were made considerably easier when she amended her request to be an ice cream cake. Now, my job was made much simpler.

Fruit purées on their own are intensely colorful. Made into a sorbet, they retain that vibrancy. Fruit-based ice creams or sherbets, though, pale in comparison (ha ha). So my plan was to stick with as many dairy-free sorbets as possible to get the brightest possible colors.

Dr. S suggested not to follow the rainbow but to alternate colors to maximize contrast. So here are the flavours we planned and made (top-to-bottom in the photo above):

1. vanilla ice cream
2. raspberry sherbet
3. kiwi-lulo sorbet
4. blackberry-blueberry sorbet
5. mango sorbet

To make an easy-to-slice ice cream cake, I lined two 8.5×4.5” loaf pans with clingfilm, and made 1 to 1.5 quarts of each flavour. After spreading each flavour in the pans, I covered them with more clingfilm, then put them in the freezer for at least 4 hours.

I used the vanilla ice cream recipe from the Van Leeuwen cookbook. It has a suggestion that I hadn’t seen before: pulverizing a vanilla bean with the cream in a Vitamix, before heating and infusing it. This worked out well for me, because the beans that I have are dried out.

For the raspberry layer, I used the raspberry sherbet recipe from Cook’s Illustrated. This is egg-free so is a bit easier to make than ice cream, as you don’t have to make a custard. For all of the other layers, I used a blend of frozen purees (I got the lulo and blackberry at a Latin grocery) as well as fresh fruit, making up 3 cups in total. I combined that with 1 cup of rich simple syrup.

I learned a few lessons while making this ice cream cake. To get even layers, consider the shape of the pan: a pan with angled sides is narrower at the bottom, so use a bit less. Also, ensure that each flavor batch you’re making has the same yield: the mango recipe I made only produced 0.75 quart (whereas the others were about 1 to 1.5 quarts). Slicing this cake was a snap, since the sorbets don’t freeze solid. To ensure success, dip your knife in hot water, and clean between slices.