In mixing bowl, cream together butter and sugar. Add egg, vanilla; mix well. Combine flour, baking powder and salt; add to creamed mixture and mix well.
Put dough into cookie press with desired plate; form cookies onto ungreased cookie sheets. Bake at 375 degrees for 6-8 minutes or until set, not brown (this part is important! DO NOT OVER COOK!). Cool on wire racks.
Beat together butter, vanilla and 2 cups powdered sugar in mixing bowl. Add milk. Continue adding sugar in 1/2 cup increments until desired consistency is reached. Add food coloring to all or a portion of frosting and frost cookies. Enjoy!