1Beat butter and sugars together in large mixing bowl until light and fluffy. Add eggs, milk and vanilla; mix well. Stir together flour, baking powder and salt in small bowl; gradually add to sugar mixture. Cover and refrigerate dough for 3 to 4 hours, until chilled.
2Preheat oven to 375°F. Prepare ungreased cookie sheets.
3On well-floured surface, roll out half of dough at a time, to 1/8 inch thickness. Cut out cookies using bat-shaped cookie cutters.
4Bake on prepared cookie sheets for 8 to 10 minutes, or until lightly browned at edges. Cool completely.
1In a bowl, with mixer at medium speed, beat confectioners' sugar, meringue powder and warm water until stiff peaks form, about 5 to 7 minutes. If icing is too thick, add a couple of drops of water. If icing is too thin, add additional confectioners' sugar; continue beating until desired consistency. Divide icing in half.
2In small bowl, cover half of icing with plastic wrap to keep from drying out; set aside. Tint remaining icing with purple food coloring. Frost the "bats" with the purple frosting, and in a pastry bag with a fine tip, use the untinted frosting for the eyes. Use the black decorator gel icing as pictured to complete the "bats."