Place the joint in a pan with enough water to cover the gammon, cover with the lid and bring to a boil and then simmer for an hour and 20 minutes. Skim surface with slotted spoon to remove any scum.
Melt the butter and add sliced leeks, celery and carrots, cook for 5-6 minutes until soft.
Add chopped garlic cloves and the dried herbs of your choice. then add stock and butterbeans and allow to simmer gently.
When the gammon has cooked break all or some of it down with a fork into a flake and add to the casserole. Taste and season, add chopped parsley. Serve with boiled or buttered mashed potatoes.