600ml chicken stock
175g waxy main-crop potatoes
100g unsalted butter
1 thin slice of cooked ham, weighing about 25g, cut into very fine dice
25g shallots, finely chopped
85ml dry vermouth, such as Noilly Prat or Martini
100g button mushrooms, thinly sliced
2 teaspoons lemon juice
1 tablespoon truffle oil
750g brill fillet, skin on, cut into 8 pieces
1 tablespoon chopped parsley
Sea salt and freshly ground black pepper
Put the chicken stock into a pan to boil until reduced by half. Set aside. Peel and slice the potatoes as thinly as you can and then cut them across into thin matchsticks. Melt half the butter in a frying pan that is large enough to hold all the pieces of fish in one layer. Add the potatoes, ham and shallots and cook gently for 4 – 5 minutes. Add the vermouth and reduced chicken stock and simmer for about 8 minutes, until the potatoes are almost, but not quite, cooked. You can prepare the dish to this stage some time in advance if you wish.
Stir the mushrooms, lemon juice, truffle oil and some salt and pepper into the pan and then rest the pieces of brill on top, skin side up. Cover and simmer for about 6 minutes or until the fish is cooked through. Lift the fish on to a plate and keep hot. Add the remaining butter to the pan and boil rapidly for 10 minutes or until the sauce has thickened and the potatoes are just beginning to break up.
To serve, peel the skin off the brill and place the fish on 4 warmed plates.
Stir the parsley into the sauce and spoon it on top of the fish.
