In a large mixing bowl, beat sugar and butter with an electric mixer on medium speed until creamy. Beat in egg yolks, milk and vanilla until thoroughly combined. In a medium mixing bowl, combine flour, cocoa and salt; add to butter mixture, beating until blended. Refrigerate dough until slightly firm (about 1 hr.). Beat egg whites in a small bowl with a fork. Shape rounded tablespoons of dough into 1 ½" balls; dip balls into egg white, then roll in nuts. Place 1" apart on parchment-lined baking sheets; press thumb into center of each cookie to make an indentation. Bake in a preheated 350° oven until set (10-12 min.); quickly remake indentations with a rounded ½ tsp. measuring spoon if necessary. Carefully remove cookies to a cooling rack to cool completely. Fill each cookie with ½ tsp. caramel topping. Place chocolate disks in zipper-closure freezer bag; microwave according to pkg. directions, squeezing bag every 15 sec. until completely melted. With scissors, snip a small corner off of bag; drizzle melted chocolate over cookies. Let chocolate set. Store cookies in an airtight container in the refrigerator for up to several days.

Tasty Tip:

• The plastic cork from a wine bottle will make perfect indentations in each cookie.