- Preheat oven to 350 degrees F. Line a 13x9x2-inch baking pan with a double-layer of foil, extending foil over the edges of the pan. Generously coat foil with nonstick cooking spray; set aside. In a large bowl, whisk together flour, cocoa powder, baking power, and salt; set aside.
- In a very large bowl, combine sugar and melted butter. Beat with an electric mixer on low speed until well mixed. Add eggs and vanilla; beat until mixed. Add cocoa powder mixture, 1/2 cup at a time, beating well after each addition (dough will be thick). Spread batter evenly in prepared pan.
- In a large microwave-safe bowl, combine caramels and milk. Microwave on 100 percent power (high) for 1-1/4 to 2 minutes or until melted and smooth, stopping to stir every 30 seconds. Immediately stir in hazelnut liqueur and 1/2 cup of the hazelnuts. Drizzle caramel mixture over top of batter in the pan.
- Bake in preheated oven for 45 minutes. Remove from oven; sprinkle immediately with chocolate pieces. Let stand for 2 minutes to melt chocolate. Using an offset spatula, spread melted chocolate over top of brownies. Sprinkle with the remaining 1/2 cup hazelnuts.
- Cool in pan on wire rack. If necessary, chill for 15 minutes to set chocolate. Using the edges of the foil, lift the uncut brownies out of the pan. Cut into bars. Makes 36 bars.
From the Test Kitchen
To toast hazelnuts (filberts), preheat oven to 350 degrees F. Spread nuts in a single layer in a shallow baking pan. Bake in preheated oven about 10 minutes or until toasted, stirring once. Place the warm nuts on a clean kitchen towel. Rub the nuts with the towel to remove the loose skins.
Place bars in a single layer in an airtight container; cover. Store in the refrigerator for up to 3 days.