Brown the Butter: In a medium saucepan over medium heat, melt the butter. Continue cooking, stirring frequently, until the butter starts to foam and turn golden brown, which should take about 5-7 minutes. Remove from heat and let it cool slightly.
Mix Sugars and Butter: In a large mixing bowl, combine the warm browned butter, brown sugar, and granulated sugar. Beat together until well combined and smooth.
Incorporate Eggs and Vanilla: Add the whole egg, egg yolk, and vanilla extract to the sugar mixture. Mix until the ingredients are fully incorporated.
Combine Dry Ingredients: In a separate bowl, whisk together the flour, baking soda, salt, and cinnamon (if using).
Combine Wet and Dry: Gradually add the dry ingredients to the wet mixture, mixing until just combined. Be careful not to overmix.
Add Pecans: Fold in the toasted pecans gently into the cookie dough.
Chill the Dough: Cover the bowl with plastic wrap and refrigerate the dough for at least 30 minutes to help the cookies hold their shape while baking.
Preheat Oven: Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
Shape Cookies: Using a cookie scoop or spoon, portion out the dough and roll it into balls. Place them on the prepared baking sheet, spacing them about 2 inches apart.
Bake: Bake for 10-12 minutes, or until the edges are slightly golden. The centers may look under-baked but will set as they cool.
Cool: Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.
Notes
Chilling the dough helps the cookies maintain their shape.