Preheat oven to 200°C. Lightly grease a 20cm x 30cm lamington pan.
Place flour, baking powder and sugar in a bowl with a pinch of salt flakes and stir to combine. Rub in the butter with your fingertips. Using a butter knife, gradually ‘cut’ the sour cream into the flour to form a soft dough, then use the butter knife to stir in the milk.
Turn out onto a clean work surface and gently knead together (do not overwork the dough). Pat out to a 2cm-thick rectangle and, using an 6-8cm pastry cutter, cut out 10-12 rounds, gently re-kneading dough if needed.
Place scones on prepared tray and bake for 25-30 minutes until golden and cooked through. Cool slightly before serving. Halve scones and spread with mixed citrus marmalade. Serve with double cream.
