In one large bowl add flour, baking soda and salt and set aside.
Melt the butter, then add to another large bowl, or the bowl of an electric mixer.
Blend melted butter with both sugars, and beat (or stir vigorously by hand) until the butter and sugars are well combined and the mixture is smooth and shiny.
Add the egg, then the egg yolk, and continue to beat until fully incorporated.
Add vanilla and blend well.
Pour flour mixture slowly into the mixer, then the chocolate chips (and nuts if desired), and blend just until all the flour is incorporated.
Preheat oven to 350*F and move the bowl of cookie dough to the fridge for 10-15 minutes (while the oven heats up).
Line 2 baking sheets with parchment paper.
Scoop the batter (using a 2 tablespoon cookie scoop) onto the parchment paper lined baking sheets. If the dough is too soft, move the entire baking sheet (with the cookie dough on it) to the fridge for an additional 10-15 minutes. The cookie dough should be somewhat firm before baking, or the cookies will turn out very flat.
Bake cookies, one baking sheet at a time for 10-12 minutes (I usually bake mine for 10 minutes).
Remove the cookies from the oven when the edges of the cookies are just BEGINNING to get golden brown, and the centers of the cookies appear slightly under-baked.
Allow the cookies to cool about 5 minutes on the baking sheets, and they will continue to cook, and firm up. Once partially cooled, carefully transfer cookies to a cooling rack.
Keep the remainder of the dough in the fridge while you are baking the others. Keeping the dough cool will help the cookies keep their shape while baking.