Chop the bacon. Soften the butter for melting. Top and tail the beans; if they are large, cut them into small pieces. Peel, quarter and core the pears. Melt the butter in a saucepan and fry the bacon gently without browning. Add the beans and pears. Season with salt and pepper. Add enough stock just to cover the pears and beans. Bring to the boil, cover with a lid and simmer for about forty minutes. Sprinkle with parsley, and serve with boiled potatoes.