Soak the lupins with plenty of water in a large container, for example overnight.
Wash the lupins with clear water and boil them in fresh water for about 15 minutes.
Cut the onion into small pieces and sauté with oil in a saucepan or pan with a matching lid. Cut the leek and carrots (and other vegetables of your choice) and sauté with the onions with the lid closed. Pour in the tomatoes and season.
Drain the lupins and stir into the vegetable mixture.