In a mixing bowl, cream butter and sugar. Add egg and vanill, mix well. Combine the flour, baking powder and salt; add to creamed mixture and mix well.
Place the dough in a cookie press fitted with a heart plate; press dough 2 inches apart on ungreased cookie sheet. Bake at 375 for 6 - 8 minutes. or until set, but not brown. Remove to rack to cool.
Beat butter, sugar and vanilla until smooth. Blend in enough milk to make desired consistency. Add food coloring if desired.