8 oz. coarsely chopped bittersweet chocolate, such as Lindt (about 1½ cups)
1 cup chopped pecans
3 Tbsp. plus 4 cups all-purpose flour, divided, plus more for dusting
2 Tbsp. baking powder
4 tsp. kosher salt
2 Tbsp. sugar, plus more for sprinkling
1½ cups (3 sticks) cold unsalted butter, cut into ½" pieces
1 cup cold heavy cream
4 extra-large eggs, lightly beaten
1 extra-large egg beaten with 2 Tbsp. water or cream (for egg wash)
Arrange racks in top and bottom third of oven; preheat to 400°. Line 2 sheet pans with parchment paper.
Combine chocolate, pecans, and 3 Tbsp. flour in a small bowl.
Using a stand mixer fitted with the paddle attachment, beat baking powder, salt, 2 Tbsp. sugar, and 4 cups flour on low speed to combine. Add butter and, with mixer still on low speed, beat until pea-sized pieces of butter remain.
Pour cream into a glass measuring cup, add eggs, and whisk until combined. With mixer still on low speed, pour cream mixture into butter mixture and beat just until blended. Add chocolate mixture and beat just until combined (the dough will be very sticky).
Turn out dough onto a well-floured work surface and knead a few times, dusting with flour so dough doesn't stick to surface, until chocolate and pecans are well distributed. Flour your hands and a rolling pin and roll dough ¾"–1" thick. You should see lumps of butter in the dough. Cut dough with 3" cutter. Place rounds on prepared pans. Reroll scraps, cut out more rounds, and place on prepared pans. Brush tops with egg wash and sprinkle with sugar.
Bake scones, rotating pans top to bottom halfway through, until tops are lightly browned and insides are fully baked, about 20 minutes. Serve warm or at room temperature.