Soak the peas overnight in several quarts of water. Dice the ham fat and render it in a large pot over moderate heat. Add the onions and cook until wilted.

Drain the peas and add them along with the bay leaf and cold water to cover. Add the ham hock or a large piece of ham skin, bring to a boil and reduce the heat to a simmer. Cover and cook for 45 minutes, or until the peas are almost tender.

Add the rice, cover and cook for 20 minutes, adding more water if necessary, until the rice is tender. Season to taste with salt and pepper and serve.