Deluxe Chocolate Marshmallow Bars

3/4 c butter
1 1/2 c sugar
3 eggs
1 t vanilla
1 1/3 c flour
1/2 t baking powder
1/2 t salt
3 T cocoa
1/2 c chopped nuts (optional)
4 c mini marshmallows
TOPPING
1 1/3 c chocolate chips
3 T butter
1 c peanut butter
2 c crisp rice cereal

In a mixing bowl, cream butter and sugar. Add eggs and vanilla, beat until fluffy. Combine flour, baking powder, salt, and cocoa. Add to creamed mixture. Stir in nuts. Spread in a greased jelly roll pan. Bake at 350 for 15-18 min. Sprinkle marshmallows evenly over cake; return to oven for 2-3 min. Using a knife dipped in water, spread the melted marshmallows evenly over cake. Cool. For topping combine chocolate chips, butter, and peanut butter in small saucepan. Cook over low heat, stirring constantly until melted and well blended. Remove from heat, stir in cereal. Spread over bars. Chill.