PREHEAT oven to 375° F.
COMBINE flour, cocoa, baking soda and salt in medium bowl.
BEAT granulated sugar, brown sugar, butter and vanilla extract in large mixer bowl until combined. Beat in eggs. Gradually beat in flour mixture. Stir in Nestlé Hearts. Refrigerate dough for 15 minutes for easier handling. Shape dough into 1-inch balls. Place 2 inches apart on ungreased baking sheets.
BAKE for 8 to 10 minutes or until edges are set. Cool on baking sheets for 2 minutes; remove to wire racks to cool completely. Dust with powdered sugar.