Preheat oven to 350 and grease an 8" square pan.
Combine cookie mix, contents of buttery flavor packet from mix, egg and water in large bowl; stir until thoroughly blended.
Divide cookie dough in half; press half the dough evenly into bottom of pan.
Cut each milk chocolate bar into 12 sections by following division marks on bars.
Arrange chocolate sections into 4 rows, with 9 sections in each row.
Place spoonfuls of marshmallow creme on top of chocolate; spread to cover chocolate and cookie dough.
Drop remaining cookie dough by teaspoonfuls on top of marshmallow creme.
Spread lightly with back of spoon.
Bake at 350 for 25-30 minutes or until light golden brown; cool completely.