Sift the flour, salt and baking powder into a bowl and rub in the butter with your fingertips until the mixture resembles breadcrumbs. Stir in the rosemary, egg and enough buttermilk to give a soft but not sticky dough. Don't overwork the mixture.
Roll the dough out on a lightly floured surface to a thickness of 1.5 cm (¾ inch). Using a 3 cm (1¼ inch) biscuit or pastry cutter, cut out 16 rounds. Place them on a nonstick baking sheet and brush the tops with a little milk. Place them in a preheated oven, 190°C (375°F), Gas Mark 5, for 7–10 minutes, or until golden brown and risen, then transfer to a wire rack to cool.
Mix together the cream cheese, dill and chives and season with salt and pepper.
Cut the top off each scone to give a flat surface, then spread a little of the cream cheese mixture on top. Place a little smoked trout on the cream cheese mixture and garnish with a dill sprig, if liked.