Step 1

Preheat the oven to 350°F. Line two 9" round cake pans, three 8" round cake pans, or one 10" x 15" jelly roll pan with parchment. Or grease and flour the bottom (but not the sides) of the pans.

Step 2

, In a heatproof bowl, whisk together the eggs, egg yolk, 1/2 cup (99g) of the sugar, and the salt.

Step 3

, Place the bowl over a saucepan of simmering water, making sure the bottom of the bowl isn’t touching the water.

Step 4

, Whisk the mixture constantly until the sugar has dissolved and it's just warm to the touch, about 110°F. Remove the bowl from the saucepan.

Step 5

, Using an electric mixer with the whip attachment, beat the mixture on medium-high speed until it becomes very light and fluffy, about 5 minutes. It should double in volume, be lighter in color, and be very thick; the batter should fall in ribbons from the beater, mounding atop the remaining batter before gradually being absorbed.

Step 6

, In a small bowl, whisk together the flour, cornstarch, and remaining 1/4 cup (50g) sugar.

Step 7

, Using very low speed on an electric mixer fitted with the whisk attachment or a hand whisk, gently fold the flour mixture into the eggs about a third at a time.

Step 8

, In a small bowl, stir together the butter and extract. Mix about a third of the flour/egg mixture into the butter, then fold that back into the remaining batter.

Step 9

, Spoon or pour the batter into the prepared pan or pans, smoothing the surface. (This recipe makes about 600g of batter. If dividing into three 8” pans, use 200g of batter for each; for two 9” pans, use 300g of batter for each.)

Step 10

, Bake the cake(s) for 15 to 20 minutes for three 8” pans or a jelly roll pan; for two 9” pans, bake for 20 to 25 minutes. The finished cake will be light gold in color and spring back when touched lightly in the center.

Step 11

, Remove the cake(s) from the oven and cool in the pan for 15 minutes. Run an offset spatula or knife around the edges of the pan before unmolding and transferring to a rack to cool completely.

Step 12

, Once completely cool, remove the parchment paper from the bottom of the cake(s), then fill and frost as desired. The cake pictured above is filled with lightly sweetened whipped cream and sliced strawberries, topped with additional whipped cream and raspberries, and garnished with lemon zest and a sprig of thyme.

Step 13

, Store leftover cake, well wrapped, at room temperature for up to a day. Genoise will dry very quickly when left on its own; it's best to fill and finish it as soon as possible. Store any cake topped and/or filled with perishable ingredients in the refrigerator, well wrapped, for several days.