Combine butter, sugar, and egg in a large mixing bowl and beat until light and creamy. Blend in melted chocolate chips and corn syrup.
Sift together flour, baking soda and salt. Stir into chocolate mixture. Chill several hours or overnight.
Using rounded 1/4 teaspoon of dough, shape into a ball and roll in granulated sugar. Repeat for all dough and place cookies on ungreased cookie sheets. Bake at 350 degrees for 10-12 minutes. Remove each batch from oven and let stand just a few seconds. DO NOT COOL. Turn half of each batch upside down and top with a mint candy half. Top with a second cookie. Place in the freezer on a flat tray or cookie sheet to harden.
HINT: This dough becomes sticky and hard to manage at room temperature. Return remaining dough to the refrigerator between batches.