Heat the oven to 220C (200C fan) and line a baking tray with paper.
Rub the cold butter into the flour, baking powder and salt until it looks like breadcrumbs. Work quickly so the butter stays cold.
Stir in the sugar, make a well and add most of the milk. Mix with a knife or a spatula to a soft, slightly sticky dough, adding the rest of the milk only if needed.
Tip onto a floured surface and pat it out gently to about 3 cm thick. Do not roll it thin, as thickness is where the height comes from.
Cut rounds with a 5 cm cutter, pressing straight down and lifting out without twisting, as twisting seals the edges and stops them rising. Re-pat the offcuts and cut again until you have 8.
Brush the tops with milk and bake for 12 to 15 minutes until golden and well risen, then cool on a rack.
Split and fill on the day they are made. The Devon order is cream first then jam, the Cornwall order is jam first, and the argument is half the fun of a cream tea.