Preheat your oven to 400°F (200°C). Line a large baking sheet with parchment paper or a silicone baking mat to prevent sticking and ensure even browning.
In a large mixing bowl, whisk together the flour, sugar, baking powder, cinnamon, and salt until well combined. This ensures the leavening agents are evenly distributed.
Add the cold, cubed butter to the flour mixture. Use a pastry cutter or two forks to work the butter into the flour until the mixture resembles coarse crumbs with some pea-sized pieces of butter remaining. This is the secret to a flaky texture.
In a separate small bowl, whisk together the heavy cream, egg, maple syrup, and vanilla extract. Ensure the egg is fully incorporated into the liquid.
Pour the wet ingredients into the dry ingredients. Stir gently with a spatula just until a shaggy dough forms. Do not overmix, as this will make the scones tough.
Turn the dough out onto a lightly floured surface. Gently knead it a few times to bring it together, then pat it into an 8-inch disc. Use a sharp knife to cut the disc into 8 equal wedges.
Place the wedges on the prepared baking sheet. Brush the tops lightly with extra heavy cream. Bake for 15-18 minutes, or until the tops are golden brown and a toothpick inserted into the center comes out clean.
While the scones cool slightly, whisk together the powdered sugar, maple syrup, and milk to create a thick glaze. Once the scones are warm but not hot, drizzle the glaze generously over the tops.