Mexican Potato, Corn and Cheese Soup

5 medium potatoes, peeled and diced
5 cups light vegetable stock
1 tablespoon oil
1 large yellow onion, chopped
2-3 cloves garlic, crushed or minced
1 large green bell pepper, finely chopped
1 cup chopped fresh tomatoes
1 cup corn
1 small jalapeno, minced
1 teaspoon chili powder
8 ounces cheddar, grated
salt and pepper to taste

Place the potato dice in soup pot and cover with stock.
Bring to simmer and simmer gently, covered, until potatoes are just tender, about 15 minutes.
In the meantime, saute onion in oil until it is translucent. Add garlic and green pepper and saute until mixture begins to brown slightly.
Remove half the potatoes from the cooking liquid, mash them well, and stir them back into the soup pot, followed by the onion, bell pepper mixture.
Add the tomatoes, corn, jalapeno and chili powder.
Stir well and return to simmer for 20 minutes.
Sprinkle in grated cheese, a little at a time, and stir until it is fairly well melted.
Season to taste with salt and pepper and simmer another 5 minutes but do not boil.