Cream butter and sugar till light and fluffy. Beat in yolk and vanilla. Stir in the flour.
Roll in balls and place on parchment lined cookie sheets. Use the back of a round measuring spoon or your thumb to make an indentation in the middle of each cookie.
Bake at 375° for 10-12 minutes or till barely brown on the bottom. Let sit on pan for a couple of minutes, then remove to cooling racks.
Melt caramels and milk in the microwave in a small glass bowl. Fill each cookie with about half a teaspoon of caramel.
Melt chocolate chips in a ziplock bag in the microwave at half power. Drizzle over cookies.