Preheat the oven to 400F/200C. Line a large baking sheet with parchment paper or a silicone baking mat. Set aside.
In a large bowl, whisk together flour, baking powder, sugar, and salt. Cut in the butter using a pastry blender or your fingers. Alternatively, you can pulse the ingredients in a food processor. Mix until mixture resembles coarse meal and there are uneven pieces of butter throughout.
Add most of the cup of heavy cream, leaving a bit for adding if needed. Add vanilla extract and stir with a spatula or fork until dough begins to form. If dough is too crumbly, add more heavy cream as needed—up to 1 cup in total. Don’t overmix. Gently fold in your add-ins, if using.
Transfer dough to a floured surface and knead gently, about 5-6 times, until a ball forms.
For round scones: Pat dough into a 9×6-inch rectangle about ¾-inch thick. Using a 2.5-inch (6.5 cm) biscuit cutter, cut out 6 rounds. Press the leftover dough into another ¾-inch thick piece and repeat the process to get 2-3 more biscuits.
For triangular scones (easier method): Pat dough into a 9-inch (23 cm) circle about ¾-inch thick. Cut circle into 8 even wedges.
Place scones on prepared baking sheet. Brush the tops with heavy cream and sprinkle with coarse sugar. Bake for 15-18 minutes, or until golden brown. Transfer baking sheet to a wire rack and allow to cool for 10 minutes. While scones are still hot, sprinkle again with coarse sugar for extra crunchiness.
These scones are delicious either warm or at room temperature.
Scones are best eaten the same day they are made, but can be frozen for up to 1 month. If you want to serve them warm, reheat in the oven before serving.