Recipe courtesy of Rory Philipson, pastry chef at The Blue Bottle Café.
6 eggs, separated
1 whole egg
1 cup ground hazelnuts
3/4 cup sugar, divided, plus 1 additional tbsp of sugar for frosting
1/3 cup breadcrumbs
1 tsp flour
1 1/2 cups heavy cream
1 tsp vanilla extract
1. Preheat oven to 275°F. In a large bowl, beat the egg yolks and the whole egg together with a wire whisk, or rotary or electric beater until mixture is thick and light yellow. Gradually beat in ½ cup of sugar, then the nuts and the bread crumbs. Continue to beat until the mixture forms a dense, moist mass.
2. In another bowl, beat egg whites with a wire whisk or electric beater until foamy, then add the other ¼ cup of sugar, 1 tbsp at a time. Beat until the whites form stiff, unwavering peaks. With a spatula, mix about a quarter of the whites into the hazelnut mixture, then sprinkle the flour over it and gently fold in the rest of the whites. Fold until no trace of the whites remains. Do not overfold.
3. Butter and flour a 10-inch springform pan. Turn the pan over and strike it to remove any excess flour. Pour batter into the pan, smoothing the top. Bake in the center of the oven for 35-40 minutes, or until it shrinks away slightly from the sides of the pan.
4. Remove the upper part of the pan as soon as you take it out of the oven and let the cake cool. Slice horizontally into 2 equal layers. Whip the chilled cream until it begins to thicken, add the sugar and vanilla and continue to whip until the cream holds its shape. Fill the cake with the cream and cover the top as well.
5. Sprinkle leftover chopped nuts over the cake. Serve promptly.