Preheat the oven to 400°F and line a baking sheet with parchment paper.

Whisk the flour, sugar, baking powder and salt together in a large bowl.

Cut the cold butter into the flour with a pastry cutter or your fingers until the mixture looks like coarse crumbs with some pea-sized pieces.

Whisk the cream, egg and vanilla together in a small bowl, then pour it into the flour mixture.

Stir gently with a fork just until a shaggy dough comes together; stop as soon as no dry flour remains.

Turn the dough out onto a floured surface and pat it into a round about 1 inch thick.

Cut into 12 wedges with a sharp knife, or stamp out rounds with a 2.5-inch cutter, re-patting scraps once.

Transfer the scones to the baking sheet, spacing them 2 inches apart, and brush the tops lightly with cream.

Bake for 15 to 18 minutes, rotating the sheet halfway through.

Check doneness by looking for tall, golden-topped scones that sound slightly hollow when tapped on the bottom.

Cool on the sheet for 5 minutes, then move to a wire rack for 10 minutes more before splitting.

Split each scone in half, top with a spoonful of jam and a dollop of clotted cream, and serve while still a little warm.