Not everyone likes fish, but this absolutely delicious way of cooking them is almost guaranteed to change their minds.
Allow one good size chunk of fish per person (I buy haddock from the excellent fish shop in Milngavie and cut them in half). Buy a jar/tub of pesto sauce made with fresh basil from Tesco, plus cherry tomatoes and enough Boursin (or Roulade cheese) to allow for a cm. penny slice each.
Put a smear of pesto around the bottom of an oven proof dish, lay the haddock pieces on top then cover the fish with the rest of the pesto. Tuck some whole cherry tomatoes into any spaces and cover each fish portion with the slice of Boursin cheese. Bake, covered, in the oven for about half an hour.
Halibut is expensive, but for a rare treat this would make a feast for a king. Trust me, you will want to do this dish over and over again because it is so easy.