In a mixing bowl, whisk together 60 g buckwheat flour, 150 g all purpose flour, 1/2 tsp kosher salt, and 1/4 tsp baking soda. Set aside.
In a large mixing bowl, combine 100 g black sugar, 100 g granulated sugar, and 113 g unsalted butter. Once mixed, add the large egg, egg yolk, and 1 tsp vanilla extract. Mix until thoroughly combined.
Add the flour mixture to the wet mixture and mix until most flour streaks disappear. Fold in 140 g dark chocolate, chopped
Portion the dough into 12 cookies on a baking sheet (about 55g each). Cover and rest for at least 1 hour in the fridge. You can also freeze the balls of cookie dough and transfer them to a zip bag once frozen.
When ready to bake, heat the oven to 350F. Line a baking sheet with parchment paper and place the cookie dough balls at least 2 inches apart.
Bake at 350F for 12-14 mins. Once done baking, transfer the baking sheet onto a wire rack to cool. Let the cookies cool completely before removing them from the baking sheet.
