In a mixing bowl, beat the egg yolks with the sugar using a wooden spoon until pale.
The Chef’s Tip
IMPORTANT: For the sponge cake to turn out well, the egg yolks and sugar must be completely incorporated. Beat them for at least 10 minutes. As the saying goes, "Well-beaten yolks make a perfect sponge cake" 😉
Beat the egg whites until stiff peaks form (add a pinch of salt beforehand). Set aside.
Add the yeast to the egg yolks and mix well.
Add the flour and cornstarch, mixing well after each addition, and folding in a little of the beaten egg whites as needed. Finally, add the remaining beaten egg whites and fold in very gently.
Pour the batter into a well-buttered round cake pan (or sponge cake pan: a deep tart pan). Dust it with a little flour (pour a little flour into the pan and shake it so the flour covers the entire surface, then invert the pan to remove any excess flour).
Bake for about 20 minutes in a moderate oven (180°C/gas mark 6). The cake should remain soft; check for doneness by inserting a knife. Once out of the oven, shake the pan to loosen the cake; if necessary, use a knife to help loosen the edges.
Place a serving dish over the pan, then flip it over. Serve in the serving dish.
For a birthday cake
Cut the sponge cake in half horizontally.
Make a syrup with 3 tbsp of jam and 7 tbsp of water. Moisten the bottom of the sponge cake with this syrup.
"Alcoholic" version: Moisten the bottom with a syrup made from 2 tbsp of liqueur or rum, 5 tbsp of water, and 5 tbsp of sugar.
Make a pastry cream. Spread it over the bottom layer of the sponge cake.