Instructions

1. Adjust an oven rack to the center position and heat oven to 375 degrees. Line a rimmed baking sheet with parchment paper or a silicone mat.
2. In a medium bowl, whisk together the flour and baking soda and set aside.
3. In a stainless steel 10-inch skillet, melt 10 tablespoons of butter over medium-high heat. Cook swirling the pan until the butter has turned dark golden brown and has a nutty fragrance, about 3 minutes. Transfer browned butter to a large heatproof bowl. Add remaining 4 tablespoons butter and stir until melted.
4. Add brown sugar, granulated sugar, salt and vanilla to the melted butter and whisk until combined. Add egg and egg yolk and continue to whisk until smooth and no sugar lumps remain, about 30 seconds. Let the mixture stand for 3 minutes, then whisk for another 30 seconds. Repeat this process of resting and whisking 2 more times, until the mixture is thick and smooth.
5. With a rubber spatula, stir in the dry ingredients until combined, about 1 minute. Stir in chocolate candy and toffee bits until evenly distributed.
6. Roll 3 tablespoons of cookie dough into balls and place 2 inches apart on the prepared baking sheet.
7. Bake until cookies are golden brown and the edges have set, but the centers are still soft, about 12 to 15 minutes, rotating the pan halfway through baking. Remove baking sheet from the oven and let cookies set on the baking sheet for 2 minutes before transferring to a cooling rack to cool completely. Repeat this process with remaining cookie dough.