The scientific secrets to baking a perfectly moist chocolate cake

NEXT week is my daughter’s 5th birthday party, and she has high expectations for her cake. It has to be extremely chocolatey, but it must also be a “piñata cake”, meaning that when you cut into it, sweets cascade out. It will also have to be large, to serve 30 children and their chaperones.

My big worry is that it could end up very dry. To achieve the required size and the piñata effect, I will have to bake at least three large layers, but I will also have to cut out the middle of the cake, which, as…