1-First, if the hazelnuts are raw, toast them. Then chop the hazelnuts and chocolate, sifting out any tiny chocolate pieces to keep things neat.

2-Next, cream the unsalted butter, dark brown sugar, granulated sugar, and salt until smooth for that rich base.

3-Add the large egg yolk and vanilla bean paste; mix well to incorporate everything evenly.

4-Add all 3 cups of unbleached all-purpose flour at once. Mix on low speed until just combined, then increase speed until the dough forms large clumps without overworking it.

5-Mix in the chopped toasted hazelnuts and chopped bittersweet chocolate until they’re evenly distributed throughout the dough.

6-Divide the dough in half. Roll each half into a 1-1/2 inch thick, 9 inch long cylinder and wrap each log in wax paper.

7-Chill the dough logs for at least 1 hour, or up to 2 days, to help with shaping and texture.

8-Preheat the oven to 325°F once you’re ready to bake.

9-Slice the chilled dough logs into 1/2 inch thick rounds and place them on parchment-lined baking sheets. Sprinkle with flaky sea salt if you like.

10-Bake for 15-17 minutes, until the bottoms are lightly golden, keeping an eye on them to avoid overbaking.

11-Finally, cool the cookies on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely for the best results.