• 1 3/4 cups shelled hazelnuts
• 1 cup (2 sticks) unsalted butter , softened, plus more for greasing
• 1 1/4 cups sugar
• 8 eggs , separated
• 1 cup ricotta cheese
• Finely grated zest of 5 lemons  
• 1/2 cup all-purpose flour
• 5 ounces best-quality bittersweet chocolate , grated

Preheat oven to 350°F. Butter a 2-inch deep, 12-inch cake pan and line with wax paper. Roast nuts in oven until their skins are loosened, about 10 minutes. Peel skins off by rubbing hot nuts in a dish towel. Coarsely chop in a food processor.

With an electric mixer, beat butter and sugar together until pale and light. Add egg yolks one by one. In a separate large bowl, beat ricotta lightly with a fork. Add lemon zest and chopped nuts. In another large bowl, beat egg whites until they form soft peaks.

Fold butter mixture into ricotta mixture, sift in flour and fold in beaten egg whites. Spoon into prepared cake pan and bake 35 minutes, or until set.

Remove cake from pan, let sit for 5 minutes, and, while warm, cover with chocolate, which should immediately melt.