1. Preheat oven to 350°.
2. Combine 1/4 cup condensed milk, butter, and next 3 ingredients in a large bowl (batter will be very stiff). Coat bottom of a 13 x 9-inch metal baking pan with cooking spray. Press two-thirds of dough into prepared pan using fingers coated with cooking spray; pat evenly (layer will be thin).
3. Bake at 350° for 10 minutes. Combine remaining 1/2 cup condensed milk and marshmallow creme in a bowl; stir in morsels. Spread marshmallow mixture evenly over brownie layer. Carefully drop remaining dough by spoonfuls over marshmallow mixture. Bake at 350° for 25 minutes (a wooden pick will not test clean). Cool completely in pan on a wire rack.
Young Chefs can:
Measure peanut butter morsels
Help press dough into pan
Older Chefs can:
Spread marshmallow mixture over brownie layer
Drop remaining dough on marshmallow mixture