1. In a large mixing bowl, beat sugar and butter with an electric mixer on medium speed until creamy.
2. Add egg yolks, milk and vanilla; beat until thoroughly combined.
3. In a medium mixing bowl, combine flour, cocoa and salt; add to butter mixture, beating until blended.
4. Refrigerate dough until slightly firm (about 1 hr.).
5. Preheat oven to 350°.
6. In a small bowl, beat egg whites with a fork.
7. Shape rounded tablespoons of dough into 1 ½" balls; dip balls into egg white, then roll in nuts.
8. Place 1" apart on parchment-lined baking sheets; press thumb into center of each cookie to make an indentation.
9. Bake in preheated oven until set (10-12 min.); quickly remake indentations with a rounded ½ tsp. measuring spoon, if necessary.
10. Remove from oven; carefully transfer cookies to wire racks to cool completely.
11. Fill each cookie with ½ tsp. caramel topping.
12. Place chocolate discs in freezer bag; microwave according to pkg. directions, squeezing bag every 15 sec. until completely melted.
13. Using scissors, snip a small corner off the bag. Drizzle melted chocolate over cookies; let chocolate set.
14. Store cookies in an airtight container in the refrigerator up to several days.

Tasty Tip:

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