Preheat oven to 200°C (400°F) and line a baking tray with parchment paper.
In a large bowl, whisk together flour, baking powder, sugar, and salt.
Add cold butter and cut it into the flour using a pastry cutter or fingers until mixture looks like coarse crumbs.
In a separate bowl, mix sour cream, egg (if using), and vanilla extract.
Gently add wet mixture into dry ingredients and stir just until dough comes together. Do not overmix.
Turn dough onto a lightly floured surface and shape into a round disk (about 1–1.5 inches thick).
Cut into wedges or use a round cutter to shape scones.
Place on baking tray, leaving space between each scone.
Bake for 15–20 minutes, or until golden brown on top.
Let cool slightly on a rack before serving warm.
