1
: Using wooden spoon stir together graham crumbs, rice cereal, 1 1/2 cups (375 ml) marshmallows and chocolate chips. Stir in sweetened condensed milk until all ingredients are evenly coated (mixture will be quite stiff).
2
: Press into parchment-lined 9-inch (23 cm) square baking pan. Top with remaining marshmallows, pressing slightly into cookie base. Bake in preheated 350°F/180°C oven for 30 minutes. Cool completely in pan on wire rack.
3
: If you can wait, let stand several hours or overnight before cutting into squares (they will still be somewhat gooey like s’mores).