Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
In a large mixing bowl, whisk together the flour, sugar, baking powder, and salt until well combined.
Add the cold cubed butter to the flour mixture. Use a pastry cutter or your fingertips to work the butter into the flour until the mixture resembles coarse crumbs.
In a separate bowl, whisk together the heavy cream, egg, and vanilla extract.
Pour the cream mixture into the dry ingredients and gently fold with a spatula until just combined (do not overmix).
Carefully fold in the chocolate chips until evenly distributed in the dough.
Turn the dough out onto a lightly floured surface and shape it into a rectangle about 1-inch thick. Cut the rectangle into 8 equal triangle wedges.
Place the scones on the prepared baking sheet, spacing them apart. In a small bowl, whisk the egg yolk with 1 tablespoon of water and brush the mixture over the top of each scone. Sprinkle a little extra sugar on top for sweetness.
Bake in the preheated oven for 15-18 minutes or until golden brown.
Remove from the oven and let cool slightly before serving.
Notes
Serve warm with clotted cream or butter for an elegant touch.