2Trickle 1 tablespoon olive oil in the bottom of a roasting pan. Arrange chicken thighs in the pan. Mix the tomato paste and water, and spread over the chicken. Place garlic clove halves in the pan. Season chicken with salt and pepper. Arrange potatoes, tomatoes, onion, mushrooms, and pepperoncini over the chicken. Sprinkle with remaining tablespoon olive oil.
3Bake 1 1/2 hours in the preheated oven, until vegetables are tender and chicken juices run clear. Periodically pour a little water into the pan if it starts to get dry.