Cream the butter, sugar, and egg. Add the remaining ingredients (not the marshmallows) and blend until smooth. The batter will be thick. Drop by teaspoons onto a greased cookie sheet. Bake at 350 degrees for about 8 minutes. Pull the pan out of the oven and carefully put three miniature marshmallows on each cookie gently, pressing them into the cookie. Bake an additional 2 minutes. Remove the oven and cool completely. Frost with your favorite chocolate cream cheese frosting.