1 tablespoon olive oil
1 medium onion, finely chopped
1/2 cup fresh mushrooms, sliced
1/4 cup green bell peppers, thinly sliced
1 cup stewed tomatoes, undrained
1 cup beef stock
8 ounces pepperoni, thinly sliced
1/2 teaspoon dried basil
1/2 teaspoon dried oregano
1 dried bay leaf
Salt and pepper, to taste
1 cup mozzarella cheese, shredded

Warm olive oil in a large, deep skillet over medium heat. Saut?onion, mushrooms, and green bell peppers until soft, but not browned. It usually takes about 3 to 5 minutes for the onions to become translucent.

Add stewed tomatoes, beef stock, pepperoni, basil, oregano and bay leaf. Continue to warm until the mixture is heated through, making sure to stir occasionally. Discard the bay leaf. Add salt and pepper to taste.

Ladle the soup into ovenproof bowls and sprinkle with shredded mozzarella cheese. Microwave until the cheese melts and is bubbly.