Heat oven to 325 F and line 2 sheet pans with parchment paper.
Combine melted butter and sugars together in stand mixer and beat with paddle for about 2 minutes.
Mix dry ingredients in a separate bowl.
Beat together egg and yolk in a separate bowl. Add vanilla.
Add egg mixture to sugar mixture. Beat mixture thoroughly about 2 minutes.
Add flour mixture and blend all together on low. The dough should be relatively stiff, you may need to add another tablespoon of flour
Finally, mix in chocolate chips.
Form into 2 tablespoon balls, or use an ice cream scoop, Place on parchment lined cookie sheet.
Ideally place in the refrigerator overnight, or at least for a couple of hours. If you can’t wait, well just go ahead and bake they will spread a bit more.
Bake 12-14 minutes, until slightly brown along edges.