Heat the oven to 425°F (220°C). Line a baking sheet with parchment paper.
In a large bowl, whisk together the all-purpose flour, baking powder, fine salt, and granulated sugar.
Add the unsalted butter and rub it into the dry ingredients with your fingertips until the mixture looks like fine, sandy crumbs and no visible butter chunks remain; work quickly to keep the butter cold.
Make a well and pour in the whole milk. Stir with a fork until the dough just comes together with no dry patches; tip it onto the lined sheet and gently pat into a 1-inch-thick round without kneading.
Using a 2–2.5-inch round cutter, press straight down (don’t twist) to cut out scones and place them on the sheet, close but not touching.
Gently press the scraps together and cut again until all the dough is used; aim for 8 scones total.
Brush the tops (not the sides) with the beaten large egg.
Bake until well risen and golden on top, 12–15 minutes; the bottoms should sound hollow when tapped.
Cool 5 minutes, then split and serve warm with clotted cream and strawberry jam.