MICROWAVE 1 cup morsels in medium, uncovered, microwave-safe bowl on HIGH (100%) power for 1 minute; STIR. Morsels may retain some of their original shape. If necessary, microwave at additional 10- to 15-second intervals, stirring just until morsels are melted. Cool to room temperature.
COMBINE flour, baking powder and salt in small bowl. Beat granulated sugar, butter and vanilla extract in large mixer bowl. Beat in melted chocolate. Add eggs one at a time, beating well after each addition. Gradually beat in flour mixture. Stir in remaining morsels. Cover; refrigerate just until firm.
PREHEAT oven to 350° F.
SHAPE dough into 1 1/2-inch balls; roll in powdered sugar. Place on ungreased baking sheets.
BAKE for 10 to 15 minutes or until sides are set but centers are still slightly soft. Cool on baking sheets for 2 minutes; remove to wire racks to cool completely.