Preheat oven to 375 degrees F. Line two baking sheets with silicone mat or parchment paper.

Melt 10 tablespoons of the butter (sliced to ensure even melting) in a small skillet, swirling the pan as it melts and browns. It should be browned only a couple of minutes after the butter is completely melted. Meanwhile, place the rest of the sliced butter into a small bowl. When the brown butter is ready, pour it over the butter in the mixing bowl and stir until all of the butter is melted together. (Do not use the stand mixer bowl for this step, or any stainless steel bowl, as the heat from the brown butter will not cool enough and will cause the cookies to bake unevenly.)

Combine both sugars, salt and vanilla to a large mixing bowl (this can be the stand mixer bowl). Add the melted butter and beat until everything is incorporated. Add the egg and egg yolk, and continue to beat at medium speed until smooth and no sugar granules appear.

Allow the mixture to rest for 3 minutes while you use a separate bowl to whisk together the flour and baking soda; set aside. After 3 minutes is up, come back to the sugar/butter mixture and beat at high speed for 30 seconds. Repeat this process of resting and beating for 2 more times until the mixture is thick and smooth.

Stir in the flour and baking soda until just combined. Fold in the chocolate chips and toffee bits.

Use a medium sized cookie scoop to spoon the cookie dough onto the baking sheets, spacing 2 inches apart. Bake for 10 minutes (rotating the pans halfway through), or until the edges are crispy and insides are still soft.

Allow the cookies to rest for 5 to 10 minutes on the cookie sheets before transferring to a wire rack to cool completely.

Recipe Source: Table for Two, originally from Cook's Illustrated