Cut the meat roughly into 3cm ( ~ 1 inch) cubes. Season half of the flour with salt and pepper and use to lightly flour the meat. Heat a little oil in a large, heavy-based frying pan and fry the meat in 2 or 3 batches over a high heat until nicely browned. Set aside on a plate.
Melt the butter in a large, heavy-based pan or flameproof casserole and fry the onion and garlic for a few minutes until lightly coloured. Add the remaining flour and tomato purée. Stir over a low heat for a minute or so, then slowly add the ale and hot stock, stirring to avoid lumps forming.
Add the beef with the thyme and bay leaf. Bring back to a simmer, cover and simmer very gently (ideally using a heat-diffuser mat or a simmer plate) for about 2 hours until the meat is tender. When the meat is cooked, the sauce should have thickened to a gravy-like consistency. If not, mix a little cornflour to a paste with 1 tbsp water, stir into the sauce and simmer, stirring, for a few minutes. Leave to cool.
To make the pastry, mix the flour, salt, suet and butter together in a large bowl and make a well in the centre. Mix in enough water (about 150ml/ ⅔ cup ) to form a smooth dough and knead for a minute.
Spoon the cooled filling into 4 individual pie dishes (or a large dish) to about 1cm from the rim. Roll the pastry out on a floured surface to a 7–8 mm (1/3 of an inch) thickness. Cut out 4 discs to make pie lids (or one large lid for a big pie), about 2cm (3/4 inch) larger all round than the pie dish(es). Brush the edges of the pastry with a little of the beaten egg.
Lay the pastry over the filling, pressing the egg-washed sides onto the rim of the dish(es). Cut a 2cm (3/4 inch) hole in the centre but leave the pastry circle in position. Let rest in a cool place for 30 minutes.
Preheat the oven to 200°C/gas mark 6/ 390° F. Brush the pie(s) with beaten egg and bake for 30–35 minutes (or 40–50 minutes for a large one) until the pastry is golden. Meanwhile, for the parsley crust, melt the butter in a pan, mix in the breadcrumbs and parsley, and season with salt and pepper.
Once the pie(s) are ready, remove the pastry disc(s) in the centre and pop in the shucked oysters. Return to the oven for 10 minutes. In the meantime, heat the grill. Scatter the parsley crust over the oysters in their half-shell and grill until golden. Place over the hole in the pie and serve.