Combine butter, sugar, eggs, flour, salt, vanilla and baking powder. Spread in a greased 9x13" pan.
Bake at 350°F for 20 minutes.
Remove from oven and sprinkle with marshmallows. Bake 2 more minutes.
Immediately press down marshmallows with spatula and cool.
In saucepan, melt chocolate chips and remove from heat.
Stir in peanut butter and Rice Krispies.
Spread over cooled marshmallow layer.