- Adjust oven rack to middle position and heat oven to 375 degrees. Line 2 large baking sheets with parchment paper.
- Whisk flour and baking soda together in medium bowl; set aside.
- Heat 10 of the 14 tblsp of butter in 10-inch skillet over medium-high heat until melted, about 2 minutes. Continue cooking, swirling pan constantly until butter is dark golden brown and has nutty aroma, 1 to 3 minutes.
- Remove skillet from heat, and using heatproof spatula, transfer browned butter to large heatproof bowl. Stir remaining 4 tblsp butter into hot butter until completely melted.
- Add both sugars, salt, and vanilla to bowl with butter and whisk until fully incorportated.
- Add egg and yolk and whisk until mixture is smooth with no sugar lumps remaining, about 30 seconds.
- Let mixture stand 3 minutes, then whisk for 30 seconds.
- Repeat process of resting and whisking 2 more times until mixture is thick, smooth, and shiny (this is really important, and the mixture really does change color and look like frosting; it's cool and yummy).
- Using 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.
- Divide dough into 16 portions, each about 3 tblsp (or use #24 cookie scoop, which is apparently exactly the size of my ice cream scoop). Arrange 2 inches apart on baking sheets, 8 per sheet.
- Bake cookies one tray at a time until cookies are golden brown and still puffy, and edges have begun to set but centers are still soft, 10 to 14 minutes, rotating baking sheet halfway through baking.
- Transfer baking sheet to wire rack; cool cookies completely before serving (but seriously, who are we kidding? I've always eaten at least half of one before they get onto the rack.)
Source: Cook's Illustrated, May & June 2009