Preheat the oven to 140°C.
Coat the meat in seasoned flour using a polythene bag.
Fry meat in 27.5g butter in a casserole until golden and set aside.
Fry bacon until crispy, then soften onions with thyme and bay leaves.
Stir in any remaining flour and the Guinness.
Return beef to the pan with prunes, walnuts, vinegar, sugar, mustard, and stock.
Bring to a boil, cover, and braise in the oven for at least four hours.
Mix dumpling ingredients with enough stock to form a paste and season.
Boil 500ml beef stock and drop in 2cm dumplings.
Cook dumplings for 30 minutes until puffed, then add to the beef casserole.
Simmer potatoes in salted water for 15 minutes, then drain and dry over heat.
Mash potatoes until smooth and beat in butter and warm milk.
Serve the braised beef and dumplings with the mashed potato.