Preheat your oven to 425°F (220°C) and line a baking sheet with parchment paper.
In a large mixing bowl, combine the flour, baking powder, salt, and sugar. Mix well.
Add the cold diced butter to the dry ingredients and use your fingers or a pastry cutter to blend the butter into the flour mixture until it resembles coarse crumbs.
In a small mixing bowl, whisk together the heavy cream, egg, and vanilla extract.
Gradually add the wet ingredients to the dry ingredients and mix until just combined. Stir in the raisins or currants, if using.
On a lightly floured surface, knead the dough gently and pat it into a circle about 1 inch thick.
Use a sharp knife to cut the dough into wedges.
Place the scones on the prepared baking sheet and brush the tops with a little bit of heavy cream.
Bake in the preheated oven for 12-15 minutes, or until golden brown.
Let the scones cool on a wire rack before serving. Serve warm with butter, jam, or clotted cream.
