Soak the peas overnight, then drain though a sieve. Melt the butter in a pot and add the onion, garlic, celery, leeks then toss to combine. Add the thyme and bay leaves and sweat everything off. Add some ham fat from the bottom of the ham and stir in with the other ingredients. Add the soaked split peas and stock, reduce the heat and simmer for 45 minutes.

Take the soup off the heat and blitz in a blender, sieve the soup into another saucepan and return to the heat to warm. Add the ham bits and serve.