Roll out the pastry and use to line 6 individual fluted 4 in. (10 cm) flan cases. Bake blind in the oven at gas mark 6, 400°F (200°C), for 15 minutes until just set. Place 4 oysters in the bottom of each flan case. Divide the spring onions equally among the flan cases. In a bowl mix the egg yolks, cream, dill and salt and pepper. Pour into the flan cases to cover the oysters neatly. Reduce the oven temperature to gas mark 3, 325°F (160°C), and bake the tartlets for a further 20 minutes until set.