This rich, delicate cake forms the basis for many filled, frosted, and glazed cakes. A good plain gênoise is hard to beatit has an elegance that derives from its simplicity, and I even like them unadorned. Many recipes for gênoise add butter as an enrichment. Unfortunately, sometimes the extra manipulation the incorporation of the butter necessitates causes these light batters to fall. So I prefer to add a few extra egg yolks insteadthey not only help enrich the cake, they also provide greater stability to the foam, ultimately making the batter easier to prepare. This recipe originally accompanied the Strawberry Roulade .