Fish soup? cullen skink? Chowder?
I'm sure you can freeze the stock for a rainy day.
Btw, home-made mayo is FAR superiour to hellmans - I can't believe that you can cook langoustine but not make mayo?
1 egg yolk, plus a second in reserve.
half pint oil (veg or a mix with olive - pure olive is too strong)
1 tablespoon vinegar
seasoning.
Put oil in a jug, yolk in a bowl, turn your hand-mixer on and whisk the yolk, then add a DRIP of oil, then when its mixed, another drip and so on until it starts to combine. Do not stop mixing until you are sure it is combined. Once you have a jellyish mix you can add the oil in a little stream. If it goes too solid, add some vinegar.
If it curdles, get your spare yolk in a clean bowl and add teaspoons of the curdled mix to the fresh yolk while mixing constantly, then go onto oil once all the curdled mixture is gone.
Add vinegar and seasoning to taste.
Enjoy.