2 x 150-175g (5-6oz) halibut fillets, skinned and pin-boned
juice small lemon
1 large leek, shredded
50g/2oz cooked and peeled shrimps
75-100ml/3-3½fl oz crème fraîche or double cream
Heat oven to 200C/fan 180C/gas 6. Using a knob of the butter, lightly grease a small flameproof baking dish and season.
Put the halibut fillets, skinned-side up, in the dish and drizzle with half the lemon juice and 5 tbsp water. Sprinkle over a pinch of salt and cover with greaseproof paper. Bring to a gentle simmer on top of the stove before baking in the oven for 6-8 mins until just lightly springy to the touch.
Meanwhile, melt half the remaining butter in a large pan, add the leek and season with salt and pepper. Cover and cook over a moderate heat for a few mins, stirring until just beginning to soften. Add the shrimps and crème fraîche and allow to gently bubble.
Spoon the leek and shrimps onto 2 plates and top with the halibut. Quickly place the baking dish on top of the stove over a rapid heat and squeeze in the remaining lemon juice while stirring in the last of the butter before spooning over and around the fish.