The aristocrat of the sponge and foam cake world, génoise has been a popular cake layer for about 300 years. When it’s well made, it is delicate and delicious in both texture and flavor. I have strong opinions about the right way to prepare it and am not in favor of adding melted butter to the batter—it sometimes causes the batter to fall, especially when the cake is being made by an inexperienced baker. So I’ve added some extra yolks, which contribute all the tenderness and moisture that t