HEAT oven to 350°F.
MICROWAVE unsweetened chocolate and butter in large microwaveable bowl on HIGH 2 min. or until butter is melted. Stir until chocolate is completely melted and mixture is well blended. Add sugar; mix well. Blend in eggs and vanilla. Add flour; mix well. Refrigerate 1 hour or until dough is stiff.
SHAPE dough into 30 (2-inch) balls; insert lollipop stick into each ball. Place, 2 inches apart, on baking sheets sprayed with cooking spray.
BAKE 8 min. or just until firm. (Do not overbake.) Let stand on baking sheets 1 min.; transfer to wire racks. Cool completely.
MELT white chocolate as directed on package; drizzle over lollipops. Decorate with sprinkles. Let stand until chocolate is firm.