In mixing bowl, cream butter and sugar until fluffy. Add vanilla and eggs, beating well after each addition.
Combine flour, cocoa, baking powder, salt and chopped nuts. Stir into egg mixture until well combined. Spread mixture in bottom of greased 3.5 L (13 x 9") pan.
Bake at 180°C (350°F) 15-20 minutes. Sprinkle marshmallows evenly over layer in pan. Bake an additional 3 minutes. Let cool.
In small saucepan, combine chocolate chips and peanut butter. Cook over low heat, stirring constantly, until melted. Stir in cereal and spread mixture evenly on top of cooled marshmallow layer. Refrigerate 2 hours or until firm. Cut into bars.
In keeping with good allergy practices, we remind you to be aware of allergens and to check labels on any packaged goods used. This recipe has been tested using Kellogg's* products. Results with other products may vary.