Liberally mist a flameproof, non-stick cooking dish or pan with cooking spray (or a tablespoon of olive oil).

Warm over medium heat on the hob.

Add the onions and fry for 5 minutes until soft, stirring often.

Add the cooked lamb, a tablespoon of flour and a pinch of salt and pepper.

Stir together well.

Cook for two minutes, stirring often.

Pour in the wine and scrape the bottom of the pan.

Bring to a simmer and cook for 3 minutes, stirring often.

Add the carrots and potatoes. Stir.

Pour in the stock and add a splash of Henderson’s relish.

Stir well and bring to a simmer.

Simmer for 30 minutes, stirring occasionally, until the sauce has reduced.

Remove from the heat.

Stir in the mint sauce.

Leave the filling to one side while you prepare the pastry.

Roll out the pastry into two squares on a lightly floured surface. One should be big enough to fill the bottom and sides of the tin with a little hanging over it, and the other should be big enough to cover the top comfortably. 

Preheat the oven to 180 degrees C (fan-assisted). 

Grease your baking tin or pie dish with butter or margarine.

Place the larger pastry square into the tin and press into the bottom and sides gently, leaving a little hanging over the edges.

Stir the pie filling and carefully spoon it into the tin, filling the pastry as much as possible.

Cover with the other square of pastry.

Press the edges together by firmly pinching around the edges of the tin.

Trim away any excess with a sharp knife.

Use a pastry brush to brush the egg liberally on the top of the pie. 

Use a knife to stab two holes into the middle of the pastry. 

Place into the oven and cook for 30 minutes until golden brown. 

Remove from the oven and rest for a few minutes before serving.