Creamy Leek and Cheese Pie

1Cook the potatoes in a pan of boiling salted water for 10-12 minutes until just tender. Drain well.

2Meanwhile, cook the leeks in the butter (50 g) until softened, then sprinkle over the flour (2 tbsp) and stir in well. Keep cooking and stirring for a few minutes, then gradually add the milk (200 ml), stirring as you do, until you have a sauce. Stir in the cheese, mustard and parsley. Season, stir in the potatoes and tip into a pie dish.

3Roll out the pastry to pound-coin thickness. Brush a little egg around the pie dish rim and top with pastry. Trim and crimp the edges, then brush more egg over the top. Cook for 25-30 minutes until crisp and golden.