Put the peas in a pot and cover with water by 2 inches. Bring to a boil over high heat, reduce heat, and simmer for 2 minutes. Remove from the heat, cover, and let them soak for 1 hour. (Or cover the with cold water and let them soak overnight.)
Meanwhile, drain the tomatoes and reserve the liquid. Hand crush the tomatoes into a saucepan and add the sugar and 1/2 cup of the liquid. Cook over medium low heat, being careful not to let it burn, until the liquid has evaporated and the tomatoes are thick, about 30 minutes.
In a large pot over medium heat add the olive oil, onion, garlic, and ham hock. Cook until the onions are soft, about 5 minutes. Add the soaked peas and the stock and cook, covered, until the peas are tender, about 20 minutes. Add some water if you need more liquid. Remove the ham hock and fold in the tomato mixture. Taste, season with salt and pepper, and serve.