Toss the lamb pieces in flour seasoned with sea salt and black pepper.
Fry the lamb in batches in rapeseed oil until golden-brown, then transfer to a casserole dish.
Fry sliced onions until golden-brown and add them to the lamb.
Add nutmeg, allspice, rosemary, stock, and water to the pan and bring to a boil.
Simmer for 40 minutes until the lamb is tender and the liquid has thickened into gravy.
Taste and season, then allow the filling to cool for 30 minutes.
Mix the sliced apples with chopped sage and black pepper.
Make pastry by rubbing lard and butter into flour and salt until it reaches a breadcrumb texture.
Whisk the egg with water and reserve 30ml for glazing.
Add the remaining egg mixture to the flour to form a dough, knead lightly, and chill for 30 minutes.
Preheat the oven to 200°C.
Layer the lamb and apple mixtures into a 2.2 litre pie dish, using a pie funnel in the center.
Roll out the pastry 5cm larger than the dish and cut a 2cm wide ring from the edge.
Apply the pastry ring to the dish rim using the egg glaze, then cover the pie with the pastry lid.
Seal the edges, brush the top with glaze, and bake for 25 minutes until golden.
Serve hot with mashed potatoes and seasonal vegetables.