Preheat the oven to 180°C.
Peel the root vegetables for the crust and cut them into chunks. Put them into a pan of cold water and cook them until tender.
Meanwhile, grease an oven dish and scatter the fish and seafood bits around.
Finely chop the onion, red pepper and carrot.
Heat the oil in a frying pan and gently sauté the onion, pepper and carrot, then add the cayenne and spinach. When the spinach has wilted add the cream and cook for a couple of minutes. Season with salt and pepper.
Pour the creamy vegetable mixture over the fish and cook in the oven for 20 minutes.
Drain the root vegetables and mash them with the butter, using a potato masher or stick blender. Season with salt &pepper.
Take the fish dish out of the oven. Turn the oven up to 200°C or to the grill.
Scatter half of the chives over the fish. Mix the remaining chives with the mash, then spread it evenly over the fish, covering well.
Grate the cheese all over the mash, season with ground pepper, then return to the oven until golden brown - for about 10 minutes.
Serve with some chopped parsley or chives sprinkled on top.