- Heat oven to 350°F.
- Spray cookie sheet with nonstick cooking spray.
- Beat butter until creamy.
- Add brown sugar and 3 tablespoons granulated sugar; beat until blended.
- Add egg, baking soda, corn syrup and vanilla; beat well.
- Stir together flour and cocoa; beat into butter mixture.
- If batter becomes too stiff, use wooden spoon to stir in remaining flour.
- Cover; refrigerate about 30 minutes, if necessary, until batter is firm enough to shape.
- Shape dough into 1-inch balls.
- Combine ¼ cup granulated sugar and cinnamon; roll balls in mixture.
- Place balls 2-inches apart on prepared cookie sheet.
- Bake 9 to 10 minutes or until cookies are set and tops are cracked.
- Cool slightly; remove from cookie sheet to wire rack.
- Cool completely.