Baking – How to stop cupcakes from collapsing

Honey is acidic with a pH of 3.9- that's more acidic than some oranges. There is also quite a lot of honey in this recipe that will give the acid the baking soda needs to react.

In this recipe, both the egg whites and the baking soda are going to provide some leavening. Without the soda the cake will undoubtedly be a little more dense.

Additionally, even when not contributing to leavening, raising the pH will promote browning of baked goods. I think the ground almonds will give nice color but the recipe may be a little paler without the soda.

There is no soda in angel food cake and I expect this cake will also be just fine without it.

The recipe you've found looks like "crazy cake" or "wacky cake" (or "depression cake"), which is a fairly common egg-free cake. I've made it a number of times for a friend with an egg allergy and it's a very good vegan cake.

To make a vanilla version, leave out the cocoa powder and increase the vanilla extract slightly (1.5 teaspoons). There are a wide array of variations on this blog -- chocolate is the "original" (and most common version that I have seen), but vanilla, spice, lemon, and more all seem to be possibilities.