| 16 tablespoons unsalted butter |
| 1/2 cup unsweetened cocoa powder |
| 2 teaspoons vanilla extract |
| 2/3 cup all-purpose flour, sifted |
| 13 ounces semisweet chocolate, chopped into small pieces |
| 1/2 cup toasted hazelnuts |
| 6 1/2 ounces semisweet (dark) chocolate, cut into small pieces |