Roll pastry into rounds. Pile up sliced potato on about half the pastry. Put onion and/or turnip on potato. Cut meat in small pieces and spread over. Season with salt and pepper. Place a few thin pieces of potato on top to save the meat drying. Damp edges of pastry. Fold over to semi-circle and crimp edges. (Crimp by pinching the pastry with the left hand and fold over with right hand, forming a rope-like effect on the side of the pastry.) Place on an unfloured baking sheet and bake at 425°F, 220°C, gas mark 7 for 10-15 minutes; reduce the heat to 350°F, 180°C, gas mark 4 for a further thirty minutes.