Beat butter and sugar.
Add yolks and vanilla.
Add flour and salt.
Chill 30 mins.
Preheat oven to 350°F.
Shape dough into 1-inch balls.
On ungreased cookie sheet, place balls 2 inches apart. Press thumb into each ball, forming indentation.
Bake 8-10 minutes or until set.
Press on indent again if needed.
Fill with caramel and add chocolate drizzle.