Melt the butter in a large saucepan and add the onion, celery, pepper, spring onions, garlic, parsley, chili sauce, Worcestershire sauce and bay leaves. Cook over a gentle heat, stirring occasionally, for about 6 minutes. Add the evaporated milk and ketchup and continue to cook for a further 2 minutes. Remove from the heat and allow to cool. Discard the bay leaves. Preheat the oven to 350° F (180°F.) Place the beef and pork in a large bowl, add the eggs, breadcrumbs and vegetable mixture, and season. Place the mixture in an un-greased roasting dish and bake for 25 minutes. Raise the temperature 400°F and bake for a further 35-40 minutes. Serve from the roasting dish.