Sauté the onion and garlic in a heavy saucepan and add the beef and vegetables. Cook stirring until the beef is browned and pour in the stock. Bring to a boil and then simmer for about 20 minutes. Add the seashell noodles to the soup and keep cooking until they are boiled. Add some fresh thyme before serving, if desired. Alternatively, you can boil the noodles separately, and add them to the soup at the time of serving. Cooking tip: 50 ml. of red wine can be added to the soup, 1 minute before pouring the stock, for an additional kick.