01 - Preheat the oven to 400°F. Line a baking sheet with parchment paper.
02 - In a large bowl, whisk together flour, sugar, baking powder, salt, and lemon zest until evenly combined.
03 - Add cold butter cubes. Using a pastry blender or fingertips, work the butter into the flour mixture until it resembles coarse crumbs with some pea-sized pieces remaining.
04 - Gently fold in the fresh blueberries until distributed throughout the mixture.
05 - In a small bowl, whisk together heavy cream, egg, and vanilla extract until fully blended.
06 - Pour the cream mixture into the flour mixture. Stir with a spatula or wooden spoon until just combined. The dough will be slightly shaggy. Avoid overmixing.
07 - Turn the dough onto a lightly floured surface. Gently pat into a 1-inch thick circle, approximately 7 inches in diameter. Cut into 8 equal wedges and transfer to the prepared baking sheet, spacing 2 inches apart.
08 - Brush the tops of each wedge with a thin layer of heavy cream. Bake for 18–20 minutes until golden brown on top. Transfer to a wire rack to cool completely.
09 - While scones bake, set up a double boiler. In a heatproof bowl, whisk together lemon juice, lemon zest, sugar, eggs, and salt until smooth.
10 - Place the bowl over a saucepan of simmering water, ensuring the bottom does not touch the water. Whisk constantly for 8–10 minutes until the curd thickens enough to coat the back of a spoon.
11 - Remove from heat. Add butter pieces and whisk until completely melted and smooth. Strain through a fine-mesh sieve if desired. Cool to room temperature before serving.
12 - Split scones in half and serve warm or at room temperature with a generous spoonful of lemon curd.