HEAT oven to 400°F.
MIX dry gelatin mix, flour and baking powder. Beat margarine in large bowl with mixer until creamy. Add granulated sugar substitute; beat until light and fluffy. Blend in egg and vanilla. Gradually add flour mixture, beating well after each addition.
SHAPE dough into 36 (1-inch) balls. Place, 2 inches apart, on baking sheets. Flatten with bottom of clean glass.
BAKE 6 to 8 min. or until edges are lightly browned. Cool on baking sheets 1 min. Remove to wire racks; cool completely.
MELT chocolate as directed on package; drizzle over cookies. Let stand until glaze is firm.