1 1/3 cups all-purpose flour
1/2 teaspoon baking powder
1/2 teaspoon salt
3 tablespoons baking cocoa
3/4 cup butter or margarine
1 1/2 cups granulated sugar
3 large eggs
1 teaspoon vanilla extract
1/2 cup chopped nuts (optional)
4 cups miniature marshmallows
1 1/3 cups (8-ounces) semisweet chocolate chips
2 tablespoons butter or margarine
1 cup peanut butter
2 cups crisp rice cereal
Preheat oven to 350°F (175°C). Slightly grease a 17 x 11 x 1-inch jelly roll pan with cooking spray. Set aside.
Whisk together flour, baking powder, salt and cocoa in a medium mixing bowl; set aside.
In a large bowl, cream together the butter and sugar; add eggs and vanilla and beat until light and fluffy. Stir in flour mixture until just mixed; fold in nuts, if using. Spread in prepared baking pan.
Bake for 15 to 18 minutes. Remove from oven and sprinkle marshmallows evenly over top; return to oven for about 2 to 3 minutes or until marshmallows are melted.
Using a metal spatula dipped in water, spread the melted marshmallows evenly over entire bar-base. Cool.
To make the topping, combine chocolate chips, butter and peanut butter in a double boiler and melt over simmering water. Stir in cereal. Spread over bars. Allow chocolate to set before cutting into bars.