Crispy Marshmallow Brownies

1 (9 x 13-inch size) box brownie mix
1 (10 1/2 ounce) package miniature marshmallows
1 1/2 cups semisweet chocolate chips
1 cup peanut butter
1 tablespoon butter
1 1/2 cups Rice Krispies cereal

Prepare the brownie mix according to package directions, making chewy (not cake-like) brownies. Bake according to directions. Top brownies with marshmallows and return to oven for 3 to 5 minutes or until golden. Cool in the pan on a wire rack.

In a saucepan, combine chocolate pieces, peanut butter and butter. Heat and stir until the chocolate is melted. Remove from heat; stir in the cereal. Pour evenly over marshmallows. Refrigerate until topping is set. Cut into bars. Serve at room temperature.