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.
