In a large mixing bowl, cream butter and sugar until smooth. Blend eggs and vanilla.
Stir together flour, pecans, cocoa, baking powder, and salt. Gradually add dry ingredients to the creamed mixture; blend well.
Spread batter in a greased 13x9 in baking pan. Bake at 350 for 15-20 min until light brown.
Sprinkle marshmallows evenly over top. Bake 3 minutes. Cool pan on a wire rack.
In a small saucepan, melt chocolate chips and peanut butter over low heat, stirring constantly. Stir in cereal. Spread evenly over top of cooled crust. Refrigerate until firm. Cut into bars. Store in the refrigerator.