Brown the Butter: Melt unsalted butter in a saucepan over medium heat, stirring constantly until deep golden brown, about 5-7 minutes. Remove from heat and cool in a heatproof bowl.

Mix Ingredients: In stand mixer, combine cooled browned butter, brown sugar, and white sugar; beat until light and fluffy, about 2-3 minutes. Add egg and vanilla extract, mixing until incorporated.

Combine Dry Ingredients: Whisk together flour, baking soda, and salt in a separate bowl. Gradually add dry mix to wet ingredients on low speed, mixing just until flour streaks disappear.

Fold in Mix-ins: Gently fold in chocolate chips and toasted pecans using a spatula.

Prepare for Baking: Drop mounds of dough onto lined baking sheets, leaving about 2 inches between each cookie.

Bake: Preheat oven to 350°F (175°C) and bake cookies for 10-12 minutes until edges are golden.

Cool: Let cookies cool on baking sheets for 10 minutes, then transfer to wire rack to cool completely.