Heat oven to 375 degrees. In large mixer bowl blend butter, shortening, sugar and egg. Gradually add in flour. If dough does not come together, add two to three tablespoons of milk. Once flour is fully incorporated, stir in baking powder, salt and vanilla. Use only enough dough to cover each cherry. Shape cookie into a ball working quickly to avoid warming the dough. Place two inches apart on ungreased baking sheet. Bake 10 to 12 minutes. Cool.