Cream together the butter and sugars. Add the egg yolk and vanilla.
Sift together the flour and salt, and add to the butter and sugar mixture one cup at a time, until completely incorporated. Dough should have a crumbly consistency that you can easily shape into a ball.
Gently fold in the chocolate chips. You can use your mixer, but I recommend doing this with your hands, so you don’t break up the chips. Shape dough into a slightly flattened disc, wrap in plastic wrap, and chill for at least thirty minutes.
4. Roll dough onto lightly floured parchment paper, cut into shapes with a 2-inch heart shaped cutter.
5. Place cookies onto a parchment-lined baking sheet and pace in the refrigerator or freezer for about 10 minutes. This will help prevent spreading.
6. Meanwhile, preheat oven to 350°. Place chilled cookies into preheated oven and bake at 350° for 10-12 minutes or until golden brown.
7. Remove from oven and allow to cool 2 – 3 minutes. Carefully, transfer to a wire rack and allow to cool completely.