Prepare and bake brownies according to package directions in an 8 x 8 or 9 x 9 pan.

Sprinkle mini marshmallows over cooked brownies and return to the oven for three minutes.

Remove from oven and cool completely.

Melt chocolate chips and peanut butter together in a double boiler, stirring until smooth.

Stir in crisped rice cereal.

Spread chocolate mixture over cooled brownies.

Refrigerate for two hours or until completely set.

Slice and store in an airtight container.