Adjust oven rack to middle position and heat oven to 375º. Line 3 large baking sheets with parchment paper.

Whisk flour and baking soda together in medium bowl; set aside.

Heat 10 tablespoons butter in 10-inch skillet over medium-high heat until melted, about 2 minutes. Continue cooking, stirring pan constantly until butter is golden brown and has nutty aroma, 1 to 3 minutes.

Remove skillet from heat and pour browned butter in to large heatproof bowl. Stir remaining 4 tablespoons butter into hot butter until completely melted. Add both sugars, salt and vanilla to bowl with butter and whisk until fully incorporated.

Add egg and yolk and whisk until mixture is smooth with no sugar lumps remaining, about 30 seconds. Let mixture stand for 3 minutes, then whisk for 30 seconds. Repeat process of resting and whisking 2 more times until mixture is thick, smooth and shiny.

Using rubber spatula or wooden spoon, stir in flour mixture until just combined, about 1 minute. Stir in chocolate chips and nuts (if using), giving dough final stir to ensure no flour pockets remain.

Use a #40 cookie scoop, or about 1 ½ tablespoons dough, drop dough 2 inches apart on prepared baking sheets. Bake cookies 1 tray at a time until cookies are golden brown and still puffy, and edges have begun to set but centers are still soft, 8-12 minutes, rotating baking sheet halfway through baking. Transfer baking sheet to wire rack; cool cookies completely on the tray for 30 minutes before serving.