On a side note, what is your take on the sponge cakes where you mix the yokes and whites separately? How does this compare to a genoise? This seems to be the main kind of cake that Maida Heatter uses in her chocolate dessert book. As I read through one cake after another, each purporting to make a chocolate layer cake, I’m wondering, “sounds good, but why would I make this sort of cake over another?” How can I choose?
There are two basic points to consider when choosing. First, whether the eggs are whipped whole or separated. The RHC Tres Leches beats them whole, while the Cake Bible Biscuit de Savoie beats them separately. The whole egg cake has a slightly denser, finer-grained texture, while the separated-egg cake achieves the maximum volume and lightness. So choose the separated-egg technique when trying to achieve the highest, lightest volume. Sometimes this is used when incorporating heavy ingredients such as ground nuts or chocolate.
The second point to consider is whether there is added butter (or oil, or cocoa butter in the case of moist chocolate gen). I think this makes a bigger difference, flavor-wise and texture-wise, than whether the eggs are separated or whole. The more butter, the heavier and denser the texture and the more amplified the flavor.
So biscuit is lighter in texture and milder in flavor, while genoise is more fine-grained and flavorful from the butter. Biscuit also needs more syrup, and is generally slightly sweeter than genoise. Also genoise can have a wide range of butter content, from a little (genoise classique) to a lot (bittersweet cocoa-almond gen), and that changes the texture and flavor dramatically.
Back to Maida’s chocolate book, I’m guessing that she uses the separated-egg method with bar chocolate because of the cocoa butter content. Bar chocolate has a higher fat content than cocoa powder, and so needs more lift from the eggs to compensate. Cocoa butter is also more highly saturated than butter and so is heavier. It emulsifies more than butter, giving a more fine-grained cake. Choose cakes with bar chocolate when you want the flavor of a chocolate bar. Choose cakes with cocoa powder/butter when you want a more complex flavor that, to me, tastes more traditionally of “chocolate cake”.