This is my favourite way to cook fish - I'm sure I had a recipe once but I don't use one now!
Basically get a whole white fish & get your fish monger to gut it for you* - if you're squinny you can get them to cut the head off too. Your choice of veg - funnel here, but finely sliced potatoes, onion, cherry tomatoes ... The worlds your oyster (in that vein I do pop a few mussels in sometimes!) Salt & pepper, olives, lemon, herbs - various things to make it taste good! Pop some of the veg/flavourings on a bit of tinfoil then add the fish & some more veg/flavourings. Seal the tinfoil up, almost completely, then splash in some wine & seal. If you're making them for guests seal them neatly - piercing them & the scented steam coming out provides an ideal show off moment (you can always open yours a bit to check everything's cooked through). Cook at around 200 for 40 minutes or so; do check it depends on what you've added & how thinly you've sliced.
Easy peasy & tastes great.
*you could gut it yourself but why?