First, Place the potatoes in a large saucepan and barely cover with water, cook for 25 minutes until very tender but not falling apart.
Meanwhile heat a large saucepan with the butter and add in the leeks, carrot and onion and sauté gently for 2-3 minutes until they are softened completely. Season well.
Pour in the white wine and the cream and allow to come to a gentle boil.
Cook for 2 – 3 minutes, then add the fish. Gently stir once or twice and bring to simmer for a further 5 minutes.
Remove from the heat and stir in the parsley. Check the seasoning with salt and pepper.
Drain the potatoes and slice or crush them slightly using a potato masher or a fork.
Scatter the potatoes on top of the fish mixture. Sprinkle the cheese and a few slices of lemon and place in the oven for 20 -25 minutes or until the fish is cooked through and the potatoes are crispy.
Serve with some green salad leaves.