New Mexican Green Chile Stew

2 pounds lean pork, cubed
2 tablespoons vegetable oil
1 large onion, chopped
2 cloves garlic, minced
6 to 8 New Mexican green chiles, roasted
    and peeled, seeds and stems removed, chopped
1 large potato, peeled and diced (optional)
2 tomatoes, peeled and chopped
3 cups water

Brown pork in the oil. Add onion and garlic; saute for about 3 minutes. Place the pork, onion, garlic and remaining ingredients in a Dutch oven or crock pot and simmer for 1 1/2 to 2 hours or until the meat is very tender.