Oh I have a great one!!
I *think* off the top of my head its a large ham bone (the more ham left on the better), 1 onion sliced, and half a bag of split peas with about 8 cups of water? And a bit of salt. You know - I should really check my recipe!
Basically I have always found the more simple the recipe, the better it tastes. Cook it for about 2 hrs I think, and then pull all the ham off the bone and mash it up in the soup.
If you dont use a ham bone its nowhere near as nice!