Preheat the oven to 200C/400F/Gas 6. 1 Place the milk in a saute pan with the bay leaf, peppercorns and onion. Bring to a simmer and cook gently for a couple of minutes. 2 Set aside for at least 10 minutes to allow the flavours to infuse. Add the fish to the infused milk and poach for 5 minutes or until just tender. Remove from the heat and leave to cool, then lift out the fish and roughly flake the flesh, discarding any skin and bone. 3 Place in a large bowl with the prawns and herbs. Strain the poaching milk into a jug. Melt half the butter in a pan and fry the shallots for 5 minutes to soften. 4 Add the mushrooms and cook for a few minutes until tender, then stir in the flour and cook for a minute or so, stirring constantly. Remove from the heat and gradually add the poaching milk. Season, return to the heat and simmer for a few minutes. Keep stirring until thickened. 5 Stir in half of the cream and add a good squeeze of lemon, then fold into the fish mixture and season. Pour into a buttered 25cm/10in pie dish and set aside to allow a skin to form. 6 Place the potatoes in a pan of boiling salted water, cover and cook for 15-20 minutes until very tender. Drain, return to the pan to dry out and then mash until smooth. 7 Beat in the remaining butter and cream and the mustard. Season to taste. Carefully spread over the fish mixture and pull a fork across the top to make a wavy-line pattern. Bake for 30-40 minutes until bubbling and lightly golden. Serve hot. Recipe by: Food & Drink