Whisk the flour, cocoa powder, sugar, baking powder, cinnamon, and salt together in a large bowl. Grate the frozen butter using a box grater. Add it to the flour mixture and combine with a pastry cutter, two forks, or your fingers until the mixture comes together in pea-sized crumbs. Place in the refrigerator or freezer while you mix the wet ingredients.

Whisk the heavy cream, egg, and vanilla extract together in a small bowl. Drizzle over the flour mixture, add the 6 ounces of chopped chocolate, and then mix until everything appears moistened.

Pour the dough onto the counter and, with floured hands, work it into a ball as best you can. The dough will be sticky. If it’s too sticky, add a little more flour. If it seems too dry, add 1 more teaspoon of cold heavy cream at a time until it comes together. Press the dough into an 8-inch disc and, with a sharp knife or bench scraper, cut into 8 wedges.

Place scones on a plate or lined baking sheet (if your refrigerator has space!) and refrigerate for at least 15 minutes and up to 1 day.

Meanwhile, preheat the oven to 425°F (218°C).

Line a large baking sheet with parchment paper or a silicone baking mat. After refrigerating, arrange the scones 2-3 inches apart on the prepared baking sheet(s).

Bake for 5 minutes. Without removing the scones from the oven, reduce the oven temperature to 400°F (204°C) and continue baking for 16–17 minutes, or until the edges and tops are set. The scones are done when a toothpick inserted into the center comes out clean or with a few moist crumbs. Keep in mind that melted chocolate on the toothpick is not wet dough.

Remove from the oven and cool for a few minutes while you prepare the glaze.

Whisk the confectioners’ sugar, vanilla, and water together. Dip the warm scones into the glaze and place on a wire rack with a baking sheet or paper towels underneath to catch the glaze as it drips down. The glaze will set after several minutes, but you can serve the scones warm. Before serving, melt the remaining 4 ounces of semi-sweet chocolate in the microwave in 15 second increments, stirring after each increment until melted. Drizzle over the scones.

Store leftover scones at room temperature for up to 2 days or in the refrigerator for up to 5 days.