1. Heat oven to 350 degrees F.
2. Heat together butter and brown sugar in medium-size saucepan over medium-high heat until the mixture is melted, smooth and bubbly. Remove saucepan from heat. Stir in the flour, then the 1/3 cup chopped hazelnuts to make a stiff dough. Spread and press dough into 8 x 8 x 2-inch square baking pan.
3. Bake in 350 degrees F oven for 20 to 22 minutes or until top is rich golden brown and edges are firm. Cool in pan on wire rack 10 minutes.
4. Spread top evenly with the chocolate-hazelnut spread. Sprinkle with the remaining 1/4 cup chopped hazelnuts. Cut into 16 bars. Serve at room temperature or chilled.