Preheat oven to 375 degrees.
Prepare cookie sheet with parchment paper.
Whisk flour and baking soda together in bowl and set aside.
Melt 10 tablespoons of butter in 10-inch skillet over medium-high heat. Continue to cook, swirling constantly, until butter has dark brown color and nutty aroma.
Transfer browned butter to bowl and mix-in remaining 4 tablespoons of butter.
Whisk in brown sugar, granulated sugar, vanilla and salt.
Whisk in egg and yolk for 30 seconds until smooth and no lumps remain.
Let mixture rest for 3 minutes
Whisk for 30 seconds and let rest 3 minutes. Repeat this step 2 more times.
Using spoon, or rubber spatula, fold in flour mixture just until combined.
Stir in chocolate chips and nuts (if wanted).
Roll 3 tablespoons of dough into a ball and place 2 inches apart on prepared cookie sheets.
Bake for 10-12 minutes. Remove from oven when edges are just starting to turn color and center is still soft.