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 well combined.
03 - Add cold butter to the flour mixture. Using a pastry blender or your fingertips, cut the butter into the flour until the mixture resembles coarse crumbs.
04 - Gently fold in the fresh blueberries until evenly distributed throughout the dough.
05 - In a small bowl, whisk together heavy cream, egg, and vanilla extract until blended.
06 - Pour the wet mixture into the dry ingredients. Stir until just combined. Do not overmix. Turn the dough onto a floured surface and pat into a 1-inch thick circle.
07 - Cut the circle into 8 wedges and transfer to the prepared baking sheet. Brush the tops with additional cream. Bake for 18-20 minutes until golden brown. Cool on a wire rack.
08 - While scones bake, whisk together lemon juice, zest, sugar, eggs, and salt in a heatproof bowl.
09 - Set the bowl over a saucepan of simmering water to create a double boiler. Whisk constantly until the curd thickens, about 8-10 minutes. Remove from heat.
10 - Whisk in the butter pieces until smooth and melted. Let cool to room temperature before serving.