1. Heat oven to 350°F. Lightly spray cookie sheet with nonstick cooking spray or line with parchment paper.
2. 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.
3. 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 1/4 cup granulated sugar and cinnamon; roll balls in mixture. Place balls 2-inches apart on prepared cookie sheet.
4. Bake 9 to 10 minutes or until cookies are set and tops are cracked. Cool slightly; remove from cookie sheet to wire rack or slide parchment paper and cookies to wire rack. Cool completely; peel cookies from paper. Makes 40 cookies.