Boil each vegetable separately and stop the cooking when the vegetable is tender but not overcooked (shock in cold water) drain and reserve.
Boil the mussels with 1 tablespoon olive oil, stop as soon as they are open. Keep only one half of the shell (the one with the mussel of course)
Make 6 cylinders with the 3 potatoes and boil them in water with salt and saffron until tender, keep warm.
In a baking dish, add olive oil, salt pepper and place the 6 fillets of fish, add more salt and pepper and a few leaves of the herbs of your choice, cover with cling film or aluminium foil.
Warm the oven to 110ºC (270ºF) and cook the fish 30 minutes.
Reheat all your vegetables in the oven and present on a plate the way you like.
Serve with the Aioli sauce.