Place chocolate in microwave-safe bowl. Microwave on medium (50% power) for 1 minute. Stir. Microwave 30 seconds more or until softened. Stir until smooth.
Mix flour and baking soda in medium bowl.
Place butter in large bowl and beat until creamy, using a hand-held electric mixer at medium speed. Add sugar and continue beating for 2 to 3 minutes or until mixture is light and fluffy. Add egg and vanilla extract and beat well. Beat in chocolate mixture.
Add flour mixture in two additions, mixing on low speed after each addition. Wrap dough in plastic wrap and refrigerate for 30 minutes.
Preheat oven to 375°F.
Roll out quarter of dough at a time on a floured surface to 1/4-inch thickness. Cut into shapes, using a cookie cutter. Place on ungreased baking sheets and sprinkle with granulated sugar.
Bake for 8 to 10 minutes or until lightly browned at edges. Remove from baking sheets and cool on racks. Store cookies in an airtight container.