Preheat oven to 300º.
Cover 2 large baking sheets with parchment paper; secure with masking tape. Sift together 1/2 cup powdered sugar and cocoa.
Place egg whites and cream of tartar in a large bowl; beat with a mixer at high speed until soft peaks form. Gradually add granulated sugar and then cocoa mixture, 1 tablespoon at a time, beating until stiff peaks form. Add vanilla; beat until combined. Fold in chocolate chips.
Drop dough by rounded tablespoons onto prepared baking sheets to form 36 mounds. Bake at 300º for 30 minutes, rotating racks after 15 minutes. Turn oven off; cool meringues in closed oven 1 1/2 hours or until dry. Sprinkle evenly with 1 tablespoon powdered sugar. Carefully remove cookies from paper.
Note: Store cooled cookies in an airtight container for up to two weeks.