Heat 1 tbsp of the veg oil in a large, deep, flameproof casserole dish over a high heat and, once shimmering, cook the bacon pieces for 5-6 mins until crisp and golden. Remove to a bowl and set aside.

Tip the flour into a bowl, season well, then sprinkle in the mustard powder and whisk to combine. Dip the venison pieces in the flour, shake to remove any excess, then brown in the residual bacon fat in batches, adding the remaining oil in 1 tbsp additions if the pan is dry. As the venison browns, remove to a plate using a slotted spoon. Set aside. If the pan looks burnt, pour in a splash of water, scrape up any burnt bits and pour them away.

Melt the butter in the pan and, once foaming, cook the celery, carrot and red onion for 10-12 mins until starting to soften. Add the garlic and cook for 3-4 mins, then add the tomato purée. Cook for 2-3 mins more until the tomato purée starts to darken, then stir in the rehydrated porcini and soaking liquid, the red wine and beef stock. Drop in the bay leaves and thyme, then return the venison and bacon to pan. Put on the lid and cook over a low-medium heat for 2 hrs-2 hrs 30 mins, removing the lid for the final 20 mins. The meat should be very tender and the sauce reduced and glossy.

When the stew has 15 mins left, start preparing the pastry. Heat the oven to 190C/180C fan/gas 5. Roll the two pastry sheets out on a lightly floured surface until they are slightly larger than a 30cm oval pie dish. Set aside.

Season the venison stew, then tip into the pie dish. Brush some of the beaten egg around the edge of one of the pastry sheets, then sprinkle the grated cheese into the middle along with a generous pinch of black pepper. Lay the remaining pastry sheet on top and press down around the cheese to seal.

Lift the cheese-filled pastry onto the pie dish over the stew filling, and crimp along the edge to seal. Brush some beaten egg all over the pastry, then use a small, sharp knife to score a sunburst pattern from the middle out to the edge. Bake for 20-25 mins until the pastry top is deeply golden. Let the pie rest for 15 mins before serving with mash and braised cavolo nero, if you like.