Whisk flour, salt, and baking soda in a small bowl and set aside.

Warm 1/2 cup (1 stick) butter in a small saucepan over medium heat. The butter will melt, then foam and bubble, then start to brown. You will notice little brown bits forming at the bottom of the pan. Stir frequently during this process and keep your attention on the pot (read about listening cues above). You will know the butter is done when it gives off a nutty aroma and turns a golden brown (about 4 to 5 minutes). Transfer butter to a medium bowl and let cool for 1 minutes. Cut remaining 1/4 cup (1/2 stick) butter into cubes, then stir into brown butter until melted.

To the bowl with the brown butter, add both sugars and whisk until the sugar is incorporated. The mixture will look like wet sand. Add the egg and yolks and whisk until the mixture is smooth (about 30 seconds). Whisk in vanilla. Add dry ingredients to the bowl, and using a spatula, fold the dry ingredients in the wet until no dry spots remain. Fold in the toasted pecans. Cover and let chill in the fridge for at least 1 hour.

Preheat to 375°F. Set an oven rack to the middle position. Line a baking sheet with parchment paper and set aside.

Using your hands or an ice cream scoop, portion out 1.5-ounce balls, and place 2-inches apart on the prepared baking sheet (8 cookies per baking sheet). Bake until the cookies are golden brown and firm around the edges (9 to 11 minutes). Let cool for 5 minutes on the baking sheet, then transfer to a wire rack.