Method

1. Put the potatoes in a pan of cold water and add a little salt. Bring to the boil, tip in the chopped onions and garlic and cook until tender - about 20 minutes. Drain and leave to cool. Cut the potatoes into 2cm cubes and place in a bowl with the cooked onion and garlic.

2. Add the cheese, spring onions, chilli and mascarpone. Toss together, taking care not to break up the potatoes too much. Season with salt, pepper and nutmeg.

3. Preheat the oven to 180C/gas 4. Line a baking tray with non-stick parchment paper.

4. Lay one of the sheets of pastry out onto a baking tray. Arrange half the potato mixture in a sausage shape down the centre of the pastry. Brush the edges of the pastry with the beaten egg, and wrap the pastry around the potato filling.

5. Brush the top with beaten egg, sprinkle with sesame seeds and score a few air holes with a sharp knife. This gives the steam from the filling a chance to escape while baking the pastry.

6. Repeat with the other pastry sheet and remaining potato mixture to make a second pie.

7. Bake for 15 minutes and then reduce the heat to 160C/gas 2. Continue cooking until the pie is golden and the pastry is cooked through - about 25 minutes.

8. Remove the pie from the oven and allow to stand for at least 10 minutes before slicing and serving.