Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
In a large mixing bowl, combine the flour, sugar, baking powder, and salt.
Add the cold butter to the dry ingredients and use a pastry cutter or your fingers to rub the butter into the flour mixture until it resembles coarse crumbs.
In a separate bowl, whisk together the milk, egg, and vanilla extract.
Pour the wet ingredients into the dry ingredients and stir until just combined. Be careful not to overmix.
If using add-ins, gently fold them into the dough.
Transfer the dough onto a lightly floured surface and shape it into a circle about 1 inch thick.
Use a sharp knife or a biscuit cutter to cut the dough into wedges or rounds, depending on your preference.
Place the scones onto the prepared baking sheet and brush the tops with a little milk or beaten egg for a golden finish.
Bake in the preheated oven for 12-15 minutes, or until the scones are golden brown on top.
Remove from the oven and allow to cool slightly before serving.