1. Beat butter, 1-1/2 cups sugar, eggs and vanilla in large bowl until fluffy. Combine flour, cocoa and salt; gradually add to butter mixture, beating until well blended. Cover; refrigerate dough about 1 hour or until firm enough to handle.
2. Heat oven to 350°F. Shape dough into 1-1/8-inch balls; roll in sugar. Place on ungreased cookie sheet.
3. Bake 8 to 10 minutes or until set. Remove from oven. Place 3 chocolate pieces on each cookie, pressing down lightly. Remove from cookie sheet to wire rack. Cool completely. Makes about 48 cookies.