Soak the beans in water to cover for at least 8 hours or overnight. Drain the beans then place in a large pan with the bay leaves, onion and water.
Bring to the boil and boil rapidly for at least 10 minutes, then simmer for 1- 1 1/2 hours until tender. Drain and discard the bay leaves, onion and cooking liquid. Season with salt and pepper.
Heat the oil in a very large pan- I use my Le Creuset Casserole. Add the leeks, carrots and potatoes and stir to coat in the oil. Add the tomatoes, green beans, courgettes, bouquet garni and season with salt and pepper.
Pour over the boiling water to cover and simmer for 45 minutes, then add the cooked beans ( or a drained tin of beans), broad beans and peas and cook for a further 120-15 minutes.
Stir in a few tablespoons of the pistou, check seasoning and serve with the rest of the pistou and bread to accompany.