Dulce de Leche Thumbprints

Heat oven to 375°F. In large bowl, stir cookie mix, butter, flour, vanilla and egg until soft dough forms. Shape dough into 1 1/2-inch balls; roll balls in sparkling sugar. On ungreased cookie sheet, place balls 2 inches apart.

Bake 10 to 12 minutes or until edges are light golden brown. Using thumb or end of wooden spoon handle, immediately make indentation in center of each cookie. Cool 2 minutes; remove from cookie sheet to cooling rack. Cool completely.

Spoon dulce de leche into resealable food-storage plastic bag; seal bag. Cut off small corner of bag. Twist bag above dulce de leche; squeeze to pipe about 1 1/2 teaspoons dulce de leche into center of each cookie.