Peel and diagonally slice the carrots into ½-inch slices, and cut the onion into eighths. Coarsely chop the tomatoes and set aside. Heat the oil over a medium heat, add carrots, onions and garlic and sauté for 3 to 4 minutes or until softened. Add wine, tomatoes, salt and pepper and bring to the boil. Add mussels, cover and cook for 3 to 4 minutes, or until they have opened – discard any that don’t open.