HEAT oven to 400°F.
RESERVE 1 Tbsp. dry gelatin mix. Combine remaining dry gelatin mix with flour and baking powder. Beat butter in large bowl with mixer until creamy. Add granulated sugar; beat until light and fluffy. Blend in egg and vanilla. Gradually add flour mixture, beating well after each addition.
SHAPE dough into 30 (1-inch) balls. Place, 2 inches apart, on baking sheets. Flatten with bottom of clean glass.
BAKE 8 to 10 min. or until edges are lightly browned. Cool on baking sheets 1 min. Remove to wire racks; cool completely.
WHISK powdered sugar, reserved gelatin mix and milk until blended; spread onto cookies. Top with sprinkles.
Special Extra: For a festive touch, garnish frosted cookies with holiday sprinkles.
Cooking Know-How: Dip the bottom of the drinking glass in additional granulated sugar before using to flatten each of the dough balls. In addition to helping to prevent the glass from sticking to the dough, the sugar also adds a glittery look to the baked cookies.
Size-Wise: Sweets can be part of a balanced diet but remember to keep tabs on portions.
How to Store Cookies: Store in single layer in tightly covered container at room temperature.