Plain Genoise

Directions

1. 1
   1 Set a rack in the middle level of the oven and preheat to 350 degrees.
2. 2
   2 Half-fill a medium saucepan with water and bring it to a boil over high heat. Lower the heat so the water is simmering.
3. 3
   3 Whisk the eggs, yolks, salt, and sugar together in the bowl of a heavy-duty mixer. Place over the pan of simmering water and whisk gently until the mixture is just lukewarm, about 100 degrees (test with your finger). Attach the bowl to the mixer and, with the whisk attachment, whip on medium-high speed until the egg mixture is cooled (touch the outside of the bowl to tell) and tripled in volume. The egg foam will be thick and will form a slowly dissolving ribbon falling back onto the bowl of whipped eggs when the whisk is lifted.
4. 4
   4 While the eggs are whipping, stir together the flour and cornstarch.
5. 5
   5 Sift one-third of the flour mixture over the beaten eggs. Use a rubber spatula to fold in the flour mixture, making sure to scrape all the way to the bottom of the bowl on every pass through the batter to prevent the flour mixture from accumulating there and making lumps. Repeat with another third of the flour mixture and finally with the remainder.
6. 6
   6 Scrape the batter into the prepared pan and smooth the top.
7. 7
   7 Bake the genoise for about 25 minutes, or until well risen, deep gold, and firm to the touch.
8. 8
   8 Immediately use a small pairing knife to loosen the cake from the sides of the pan. Invert the cake onto a rack, then reinvert onto another rack and let the cake cool right side up on the paper. Remove the paper when the cake is cool.
9. 9
   Reduce the bake flour to 1/3 cup, increase the cornstarch to 1/3 cup, and add 1/4 cup alkalized (Dutch-process) cocoa powder to the flour and cornstarch mixture, sift.
10. 10
    Bake either the plain or chocolate batter in a 10 x 15-inch jelly roll pan that has been buttered and lined with buttered parchment at 400 degrees for about 10 to 12 minutes. Make sure the cake doesn't overbake and become to dry, especially if it is tot be rolled. (Makes on 10 x 15-inch layer.)