Clean the leeks, peel potatoes. Cut onions rings and potato cubes. Fry them in three tablespoons of olive oil, salt and when they become golden, add 1 liter of water. Simmer 20 minutes. Wash mussels. In a large pot, heat the remaining olive oil sauté briefly, add the garlic mussels and white wine, cover with a lid and stew until the mussels open. Cut the tomatoes and add them in potato soup with black beans, sauce of mussels and pepper. Cook for another half hour. During this time, take the mussels from the shells. At the end add them to the soup. Serve with freshly chopped parsley.