Porcini are one of the most prized mushrooms. They are dried for preservation and when rehydrated in water they bestow their powerful, almost meaty flavour to the liquid. This tart uses that liquid and other mushrooms, as well as the porcini themselves, so it is crammed with mushroom flavour.
Poached monkfish is quite easy to cook when entertaining as it just needs a few minutes in boiling, salted water, and can be prepared in advance.
If you are cooking this dish for quite a few people, you can lay the fish on an oiled oven tray, drizzle a little oil over the top of each fish, and cook under a hot grill for 3–5 minutes on each side or until the skin is crispy and the fish opaque all the way through.