Petits Fours au Chocolat et aux Noisettes

Name: Petits Fours au Chocolat et aux Noisettes (Chocolate-Hazelnut Cakes)
Prep time: 45 min
Total time: 45 min
Yield: Makes 20 to 30 petits fours
Cuisine: French
Ingredients: 5 large egg whites, at room temperature; 155 grams (5½ ounces) sugar; 5 large egg yolks; 115 grams (4 ounces) unsalted butter, at room temperature; 180 grams (6⅓ ounces) semisweet or bittersweet chocolate, cut into small bits; 180 grams (6⅓ ounces) semisweet or bittersweet chocolate, cut into small bits; 115 grams (4 ounces) toasted hazelnuts, finely ground; 55 grams (2 ounces) all-purpose flour