- Preheat oven to 350°F.
- Coat an 8-inch square baking pan with vegetable cooking spray; set aside.
- Cut chocolate into 1-inch pieces and place in heat-proof bowl.
- Set over low heat in small skillet containing ½-inch simmering water.
- Stir occasionally just until chocolate is melted. Remove from heat; set aside.
- In mixer bowl combine all ingredients except flour and walnuts; beat to blend thoroughly.
- Mix in flour. Spread batter in prepared pan; sprinkle with walnuts.
- Bake about 30 minutes until springy to the touch about 2 inches around edges.
- Cool on rack. Cut into 1½-inch squares.