Make the blueberry topping. Place 3 cups of blueberries in a medium saucepan (reserve the remaining 1 cup!)), then add ½ cup (100g) sugar, 2 Tbsp fresh lemon juice, and a pinch of Kosher salt. Cook, stirring occasionally, until the berries begin to break down and the sugar melts, about 5-7 minutes. Feel free to smash some of the berries a bit to help release their juices. Remove from the heat, then stir in the remaining 1 cup of blueberries. Allow this to cool while you prepare the biscuits.
Prepare the biscuits. Combine 3 cups (360g) all-purpose flour, ¼ cup (50g) sugar, 1 Tbsp baking powder, 1 tsp baking soda, 1 tsp lemon zest, and ½ tsp Kosher salt in a bowl, then whisk well. Stir in 10 Tbsp (141g) grated cold butter. (If using cubed, use your hands or a pastry cutter to work the butter into the flour until there are mostly pea-sized pieces of butter.)
Mix the wet ingredients. In a 2-cup measuring cup, whisk together ½ cup (118ml) heavy cream, ½ cup (118ml) buttermilk, 2 large (100g) eggs, and 1 tsp vanilla extract. Make a well in the dry ingredients, then pour the buttermilk mixture in the center. Use a fork or spatula to gently mix the batter until it begins to clump together to form a dough. It will be crumbly.
Form the biscuits. Turn the dough out onto a lightly floured surface, then roll it out until it’s 1-inch thick. Use a 2-inch biscuit cutter (or a large glass) to cut out biscuits. You can combine the leftover dough and re-roll it out until you’ve used all the dough.
Bake the biscuits. Preheat an oven to 400°F (205°C). Place the biscuits on a parchment lined baking sheet, then brush the tops with the remaining 2 Tbsp heavy cream. Optional: sprinkle with a little turbinado sugar if you like! Bake for 18-20 minutes, or until they’re golden brown. Cool completely on a wire rack.
Whip the cream. Place 1½ cups (355ml) heavy cream, 3 Tbsp (6g) confectioners’ sugar, and 2 tsp vanilla extract in the bowl of a stand mixer fitted with whisk attachment. Beat on medium-high speed until medium peaks form. If you prefer stiff peaks, beat it a little longer.
Assemble the shortcakes. Split each biscuit in half, then place on a plate or in a bowl. Spoon a generous amount of the blueberries on the bottom half. Top with a dollop of whipped cream, then add the top biscuit. Enjoy!