Melt butter in a 4-quart saucepan over medium heat. Sprinkle pork chops with salt and pepper on both sides. Place in saucepan. Stir in onion, and garlic. Cook 3 minutes; turn pork chops, and cook 3 more minutes. Stir in basil, tomatoes, mushrooms, milk, and soup. Reduce heat to low, cover, and simmer. After 30 minutes, turn chops, stir contents, and simmer 30 minutes more. To serve, pour sauce over chops and top with a teaspoon of sour cream on each chop.