Place the butter and chocolate in a microwave-safe bowl. Heat at half-power in 30-second increments until the butter has melted and the chocolate melts when stirred. Stir until thoroughly combined and smooth. Set aside to cool slightly.

Combine the sugar, eggs, both extracts, and the salt. Add the chocolate mixture, and mix well. Add the flour, and stir just until combined.

Reserve 3 to 4 tablespoons of nuts for the topping. Stir the remaining nuts into the batter.

Transfer the batter to the prepared pan, and spread evenly. Sprinkle the reserved nuts on top, and gently pat them down into the batter.

Bake 30 to 35 minutes, or until the brownies appear set and a pick inserted into the center comes out with a few moist crumbs.

Cool in the pan before cutting into bars.