With an electric mixer, beat the softened butter and both sugars until creamy. Beat in the vanilla, salt and egg yolk. Add flour 1 cup at a time and stir to make a dough. Stir in chips. Note: You can stir all of them in or you can stir in 1 ½ cups and save ½ cup for melting.
To make the cookies, roll dough about ¼ inch thick between sheets of wax or parchment paper. Cut into shapes. Bake on parchment lined baking sheets in a preheated oven at 350 for about 9 to 12 minutes.
If you'd like to decorate with melted chips, put the reserved ½ cup mini chips in a heavy duty freezer zipper bag. Microwave on high for 30 seconds. Carefully rub the bag a little to help melt the chips, then continue heating at 10 second intervals and rubbing bag until chips are melted. Snip a hole in the corner of the bag and squeeze melted chocolate onto the cookies.
