Place the unsalted butter in a medium saucepan over medium heat. Let it melt completely, then continue cooking, swirling the pan frequently, until the butter turns a golden brown color and emits a nutty aroma (about 5-7 minutes). Transfer the browned butter to a large mixing bowl to cool slightly.
Add the packed brown sugar and granulated sugar to the warm browned butter. Use an electric mixer or whisk to combine until smooth and creamy. Then, add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.
In a separate bowl, whisk together the all-purpose flour, baking soda, and salt. Gradually add the dry ingredients to the wet mixture, stirring with a spatula until just combined. Avoid overmixing to keep your cookies tender.
Gently fold in the chopped toasted pecans, toffee bits, and semi-sweet chocolate chips.
Cover the dough with plastic wrap and refrigerate for at least 30 minutes (optional but recommended) to help flavors meld and prevent spreading.
Preheat your oven to 350°F (175°C). Line baking sheets with parchment paper. Using a cookie scoop or tablespoon, drop dough balls about 2 inches apart on the sheet. Bake for 10-12 minutes, or until edges are golden but centers still look slightly soft.
Remove cookies from the oven and let sit on the baking sheet for a few minutes before transferring to a cooling rack. Enjoy warm or store for later.