Yield: 8 pieces

About 1/4 cup butter or margarine
1 cup firmly packed brown sugar
1 large egg
1 teaspoon vanilla extract
1 teaspoon baking powder
1/4 teaspoon salt
About 1 cup all-purpose flour
1 cup (6 ounces) semisweet chocolate chips, divided
3/4 cup coarsely chopped walnuts, divided

In a 2- to 3-quart pan over medium-high heat, melt 1/4 cup butter until it begins to brown, 3 to 5 minutes (if using margarine, melt but do not brown). Let cool 20 to 25 minutes.

Preheat oven to 350 degrees F. Butter and flour an 8-inch square pan.

Add sugar, egg, vanilla extract, baking powder, and salt; stir to mix well. Add 1 cup flour and stir until incorporated; mixture will be stiff. Stir in half the chocolate and half the nuts.

Spread batter level in prepared pan; sprinkle with remaining chocolate and nuts. Bake until edges begin to pull from pan sides and brownies are firm to touch in the center, about 30 minutes (25 minutes in a convection oven).

Cool in pan on a rack at least 30 minutes. Cut into 8 equal pieces.

Serve warm or cool.