Step 1

Place the butter in a wide and heavy-bottomed saucepan over medium-low heat. Cook for about 5 minutes, swirling the pan almost constantly, until the butter has completely melted and is a light brown color. Remove from heat and scrape the butter - and any brown specks - into a heatproof bowl. Place the bowl in the refrigerator and bring the butter back to room temperature. This will take about 2 hours.

Step 2

Once the butter is at room temperature, preheat oven to 375 degrees (F). Line 2 large baking sheets with parchment paper and set aside.

Step 3

In a medium-sized bowl whisk together the flour, baking soda, salt, and cinnamon. Set aside.

Step 4

In the bowl of a stand mixer fitted with the paddle attachment, add the chilled brown butter and both sugars; beat on medium speed for about 2 minutes, or until light and fluffy. Add in the vanilla and beat smooth. Add the eggs and egg yolk, one at a time, beating well after each addition, and scraping down the sides of the bowl as needed.

Step 5

Reduce mixer speed to the lowest setting. Gradually add in the flour mixture, stirring only until the flour begins to disappear. Add in chocolate chips, toffee bits, and pecans, stirring until evenly combined. Turn mixer off.

Step 6

Roll 3 tablespoon sized balls of dough between your palms to form a ball, then place on prepared baking sheet. Leave about an inch of room between each cookie for inevitable spreading. Continue this process until all the dough has been rolled.

Step 7

Cover the baking sheets with saran wrap and chill for at least 30 minutes, or up to 3 says.

Step 8

When ready to bake, place baking sheets in preheated oven, one at a time, and bake for 10 to 11 minutes, or until cookies are golden at the edges but still soft in the middle.

Step 9

Let cookies cool for 10 minutes on the sheet before transferring to a wire rack to cool completely.