Place the soaked bacon joint in a large lidded saucepan with the bay leaf, peppercorns, cloves, cinnamon, onion, and cider.
Add enough cold water to cover the joint by 2.5cm, bring to the boil, then simmer covered for one hour.
Pierce the meat with a knife to check tenderness and cook for 20 more minutes if necessary.
Preheat the oven to 190°C and melt butter in a large ovenproof casserole on the stove.
Fry the garlic, shallots, and peppercorns for one minute, then add carrots and celery and fry for five minutes.
Remove the skin from the bacon and place the meat on top of the vegetables in the casserole.
Cover the vegetables with 2.5cm of the poaching liquid, put the lid on, and bake for 15 minutes.
Sieve flour, salt, and mustard powder into a bowl and stir in suet, parsley, and pepper.
Add cold water to form a stiff dough and roll into large walnut-sized balls.
Add dumplings to the casserole and bake for another 25 to 30 minutes until puffed.
Slice the meat and serve with the vegetables, dumplings, and juices alongside English mustard.