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, baking soda, salt, and lemon zest until well combined.
03 - Add cold butter cubes to the flour mixture. Using a pastry cutter or fingertips, work the butter into the flour until the mixture resembles coarse crumbs with some pea-sized pieces remaining.
04 - Gently fold in the blueberries until evenly distributed throughout the mixture.
05 - In a small bowl, whisk together heavy cream, egg, and vanilla extract until fully blended.
06 - Pour the wet mixture over the flour mixture and mix gently with a fork just until the dough begins to come together. Do not overmix to ensure tender scones.
07 - Turn the dough out onto a lightly floured surface and gently knead once or twice to bring it together. Pat into a 1-inch thick round disc.
08 - Cut the disc into 8 wedges and transfer to the prepared baking sheet, spacing them 2 inches apart. Brush tops lightly with additional cream.
09 - Bake for 18 to 22 minutes, until scones are golden brown and a toothpick inserted in the center comes out clean. Transfer to a wire rack to cool slightly.
10 - In a small saucepan over medium-low heat, whisk together eggs, sugar, lemon juice, and lemon zest until smooth.
11 - Cook the mixture, whisking constantly, until it thickens and coats the back of a spoon, about 5 to 7 minutes. Do not let it boil or the eggs may scramble.
12 - Remove from heat and whisk in butter pieces until smooth and melted. Strain through a fine sieve into a bowl. Let cool to room temperature before serving.
13 - Serve scones warm or at room temperature, accompanied with homemade lemon curd on the side or dolloped on top.