Heat oven to 350°F. On ungreased cookie sheet, place dough rounds 2 inches apart. Bake 12 to 15 minutes or until edges are light golden brown. Remove from cookie sheet to cooling rack to cool completely.
Meanwhile, to make hats, remove creme from sandwich cookies, and attach miniature peanut butter cup to one half of sandwich cookie, using small amount of vanilla frosting. Continue for remaining hats.
Cut marshmallows in half, and place one half on top of each cookie, cut side down. In small microwavable bowl, microwave remaining frosting uncovered on Medium (50%) 20 to 40 seconds, stirring halfway through, until slightly warm.