Tripe, Butter Beans, and Smoked Bacon
Rinse the tripe several times, then bring to boil in salted water. Remove immediately and drain in a colander.
In a large pot, place the tripe, onion, carrots, leek, thyme, and bay leaves. Fill with enough chicken stock to cover by about 1 inch. Add the bacon skin along with any bacon trim, check the seasoning, and add mace. Bring gently to a boil and reduce to a simmer. After 2 hours, check the tripe (it should be soft enough to pierce but not melted into stock). When ready remove the tripe and chill in the fridge. Pass the liquid through a fine sieve and refrigerate.
In a separate pot, bring butter beans and water to a boil, then drain through a colander. Return to the pot with garlic and simmer until tender. Remove beans (discarding garlic) from heat and reserve water.
Cut tripe into 1-inch pieces. Dice the skinless bacon and fry in a pot until golden, then reserve. Add butter and onions to pot and sweat until tender. Season carefully and add bacon, tripe, butter beans, and reserved tripe stock. Simmer gently, then season with salt and pepper. Add mustard and quickly wilt watercress before serving.