In a large bowl, whisk together the flour, sugar, lemon zest, baking powder, and salt. Grate the frozen butter using a cheese grater, then add it to the dry ingredients. Use a pastry cutter, two forks, or your fingers to mix until the texture resembles pea-sized crumbs. Place the bowl in the freezer while preparing the wet ingredients.

In a small bowl or liquid measuring cup, whisk together 1/2 cup of heavy cream, the egg, and vanilla extract. Remove the flour mixture from the freezer, drizzle the cream mixture over it, and add the blueberries. Gently mix with a spatula or wooden spoon until the dough just comes together and looks evenly moistened.

Lightly flour a clean work surface and transfer the dough onto it. With floured hands, shape it into a ball. The dough will be sticky—if needed, add a little extra flour. If it seems too dry, mix in 1–2 more tablespoons of heavy cream. Flatten the dough into an 8-inch disc, about 1 inch thick. Use a sharp knife or bench scraper to cut it into 8 equal wedges.

In a small bowl, stir together the remaining 1 tablespoon of cream with the water, then brush this mixture over the scones. For added sweetness and crunch, sprinkle coarse sugar on top. This can be done before or after chilling.

Place the scones on a plate or a lined baking sheet and refrigerate for at least 15 minutes or up to 24 hours. If chilling for more than an hour, lightly cover them.

Preheat the oven to 400°F and line a large baking sheet with parchment paper or a silicone baking mat. Arrange the chilled scones on the baking sheet, leaving 2 inches of space between each.

Bake for 20-25 minutes, or until the edges are golden brown and the tops are lightly browned. Remove from the oven and let them cool for about 5 minutes before adding icing.

To make the lemon icing, whisk together the confectioners’ sugar and 2 tablespoons of lemon juice in a small bowl. If a thinner consistency is desired, add an extra tablespoon of lemon juice. Drizzle the icing over the warm scones. Serve and enjoy!