Heat some oil in a casserole dish over a medium heat. Add the bacon and sauté until crispy. Transfer to a clean plate and set aside.
Toss the diced beef in the seasoned flour and dust off the excess. Add a little more oil to the casserole dish and fry the beef in batches until browned on all sides. Place the seared beef pieces on the clean plate with the bacon and set aside.
Add a little more oil to the casserole dish and gently sauté the onion until just softened but not browned. Deglaze the pan with some stout.
Return the beef, bacon and their juices to the casserole dish and stir in the red pepper, tomatoes, tomato purée, sugar, mustard and bouquet garni and season with salt and freshly ground black pepper.
Add the rest of the stout. Bring to the boil, cover, reduce the heat and then simmer over a low heat for about 1½ hours or until the meat is tender and the sauce thick, stirring from time to time.
Meanwhile, prepare the pastry. Sift the flour and salt into a large bowl. Add the diced butter and rub with your fingertips until the mixture resembles fine breadcrumbs. Add the baking powder and mix well. Stir in the potatoes and pour in just enough cold water to form a soft dough. Turn it out on a floured surface and knead very lightly. Wrap in clingfilm and leave to rest for 30 minutes in the fridge. (The pastry can also be made several hours in advance and stored in the fridge until you’re ready to use it.)
During the last 10 minutes of the filling’s cooking time, heat a medium frying pan with a little butter, add the mushrooms with some salt and freshly ground black pepper and sauté for about 4 to 5 minutes. Then add to the casserole and simmer for 3 to 4 minutes. Check the seasoning, adding more salt and pepper if required. When you are ready to make the pies, remove the bouquet garni from the beef.
Choose 6 ramekins (or more, depending on their size). Preheat the oven to 210°C/fan 190°C/Gas 7.
Carefully roll out the pastry on a floured surface – it shouldn’t be too thin. Using a large cutter, cut out 6 or more discs 2cm larger than the ramekins. Spoon the beef into the bowls, brush the edges with egg wash and place the pastry discs on top. Crimp the edges. Re-roll the pastry trimmings and use to cut out leaves. Attach these to the top of the pies with egg wash. Make a small hole in the top of each disc for the steam to escape. Leave in the fridge to rest for about 20 minutes.
Then brush the pastry with egg wash and transfer the ramekins to the oven for about 18 to 20 minutes or until the pastry is golden and baked.
Rest for about 5 minutes before serving with a fresh garden salad.