01 - Preheat the oven to 400°F. Line a baking sheet with parchment paper.
02 - In a large bowl, whisk together the flour, sugar, baking powder, baking soda, salt, and lemon zest until evenly distributed.
03 - Add the cold butter to the flour mixture. Cut it in using a pastry cutter or your fingertips until the mixture resembles coarse crumbs with some pea-sized pieces remaining.
04 - In a separate bowl, whisk together the heavy cream, egg, and vanilla extract until fully combined.
05 - Pour the wet ingredients into the dry ingredients and stir gently with a spatula until just barely combined. Do not overmix.
06 - Gently fold in the fresh blueberries, being careful not to crush them.
07 - Turn the dough onto a lightly floured surface and gently pat it into a 1-inch-thick circle. Cut into 8 equal wedges and transfer to the prepared baking sheet, spacing them 2 inches apart.
08 - Brush the tops with a little extra heavy cream. Bake for 18–22 minutes, or until golden brown. Let cool on a wire rack for at least 10 minutes.
09 - In a small saucepan, whisk together lemon juice, lemon zest, sugar, and eggs until smooth.
10 - Add butter and cook over medium-low heat, stirring constantly with a heat-proof spatula, until thickened enough to coat the back of a spoon (about 8–10 minutes). Do not let it boil or the eggs may scramble.
11 - Remove from heat and let cool completely; the curd will thicken further as it cools.
12 - Serve scones warm or at room temperature with a generous spoonful of lemon curd.