Preheat oven to 325 degrees.
Combine the dry ingredients (flour, baking soda, salt) and sift together. (I occasionally skip this step and they still turn out great.)
Melt the butter and let cool slightly. The butter should be opaque.
Add the brown and white sugars. Cream the butter and sugars together.
Beat in the vanilla and then add in the egg and egg yolk and continue beating until the mixture is light and creamy.
Add in the dry ingredients and mix just until combined.
Stir in the chocolate chips. Put the dough in the refrigerator for a good hour until it is nicely chilled.
Drop cookie dough 1/4 cup at a time onto a lightly greased cookie sheet. Space cookies about 3 inches apart.
Bake for 12 to 15 minutes in the preheated oven. The cookies are done when the edges are golden and the center looks slightly under baked.
Let the cookies cool on the baking sheet for at least 5 minutes and then transfer to a wire racks to finish cooling.
Store in an airtight container for up to a week.