1/4 c. butter
1 (6 oz.) pkg. semi-sweet chocolate chips
3/4 c. sugar
2/3 c. all-purpose flour
1/2 tsp. vanilla
1/4 tsp. baking powder
1/4 tsp. salt
2 eggs
1/2 c. chopped nuts (optional)
1 c. chilled chocolate chips, peanut butter chips or white chocolate chips (optional)

Heat oven to 350 degrees. Grease bottom only of 8 x 8 x 2 inch pan. Heat butter and 1 package chocolate chips in a saucepan over low heat, stir constantly until melted; remove from heat. Stir in remaining ingredients, except nuts and 1/2 cup chocolate chips, until smooth. Stir in nuts and chocolate chips spread in pan with a rubber spatula. Bake until center is set, about 30 minutes. Let cool then serve.