Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper.

In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, baking powder, salt, and instant espresso powder. Ensure there are no clumps of espresso powder.

Add the cold, cubed unsalted butter to the dry ingredients. Use a pastry blender, two forks, or your fingertips to cut the butter into the flour mixture until it resembles coarse crumbs with some pea-sized pieces of butter remaining.

In a separate small bowl, whisk together the 1/2 cup heavy cream, 1/4 cup cold milk, and vanilla extract.

Pour the wet ingredients into the dry ingredients and mix with a spatula or your hands until just combined. Do not overmix; the dough will be shaggy. Gently fold in the chocolate chips until evenly distributed.

Turn the dough out onto a lightly floured surface. Gently bring the dough together and pat it into a round disc, about 7-8 inches in diameter and 1 to 1.5 inches thick. Avoid overworking the dough.

Using a sharp knife or a bench scraper, cut the disc into 8 wedges (like a pizza). Carefully transfer the wedges to the prepared baking sheet, spacing them about 1 inch apart.

Brush the tops of the scones with 1-2 tablespoons of extra heavy cream for a golden-brown finish.

Bake for 16-20 minutes, or until the tops are golden brown and a toothpick inserted into the center comes out clean. Let the scones cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely.

While the scones are cooling, prepare the glaze (if using). In a small bowl, whisk together the powdered sugar, 1/2 teaspoon instant espresso powder, and 2 tablespoons of milk or cream. Add more milk/cream 1 teaspoon at a time if needed, until you reach a smooth, drizzling consistency.

Drizzle the cooled scones with the coffee glaze before serving.