Heat oven to 350°F. Line 12-inch pizza pan with foil; grease foil with shortening. Cut cookie dough into 1/4-inch slices; arrange evenly in pan. With floured fingers, press slices to form crust.
Bake 16 to 20 minutes or until deep golden brown. Immediately sprinkle marshmallows evenly over warm base. Bake 1 to 2 minutes longer or until marshmallows just begin to puff.
Use foil to lift crust from pan. Carefully remove foil from crust; place crust on serving platter or tray. Sprinkle with chocolate chips, butterscotch chips and decors.
In small microwavable bowl, microwave frosting uncovered on High 10 to 15 seconds or until thin enough to drizzle. Drizzle frosting over cookie pizza. Cut into wedges or squares.