Trim off and discard any fat from the chicken or pork. Place all the ingredients in a big pot and cover with cold water. bring to the boil and skim off any scum that rises to the surface. Reduce the heat to a very gentle simmer. After an hour remove the spring onions and cook for a further 2 hours on a low simmer. Strain and store in the fridge for 3-4 days or freeze for up to a month.