Use as much seafood as you like, but...
A minimum of 2 gambas per person, peeled (save heads and carcasses) Sauté gambas very quickly in a little olive oil, until they turn red.
Slice some scallops quite thick (½cm.) and grill very quickly (min. two or three slices per person).
Slice open small calamars, beat well both sides and grill quickly. Slice 1cm. thick (three or four slices each).
Steam open mussels in chardonnay, plus finely chopped small onion, a good pinch, fennel seeds, parsley and thyme. Should be open in just one min. after boiling. (you must cover the pan) Shell.
Put the juices in a saucepan with gambas shells. Bring to the boil and cook for ten mins., and strain. Save.
Now you need approx. 1ocl. of the juices (reduce if needed) and one yolk per 2 people (+ one extra yolk per four) for the gratin. Bring to the boil, beat egg yolks and pour on boiling juices while beating. Transfer to a saucepan and thicken whilst continuously stirring on moderate heat, until you can coat the back of a wooden spoon. Season this sabayon, if necessary.
Divide seafood in individual gratin dishes or use one big one; coat with the sabayon , and put in hot oven for 5 mins., and then transfer to under the grill until brown.