Heat oven to 375°F. For each cookie cup, wrap heaping teaspoonful cookie dough around 1 candy bar, enclosing it almost completely and forming ball. Place in 1 3/4-inch paper baking cups placed 1 inch apart on ungreased cookie sheets.
Bake 8 to 12 minutes or until golden brown. (Centers of cookies will sink slightly.) Cool 1 minute; remove from cookie sheets to cooling racks. Cool completely, about 15 minutes.
Spoon about 3/4 cup frosting into pastry bag with a star tip. Pipe frosting on top of each cookie cup.