5 fl oz (150 ml) dry white wine
500g ready-made mashed potato
Pre-heat the oven to gas mark 7, 425°F (220°C).
Heat the wine and stock in a medium saucepan, add the bay leaf and some seasoning, then cut the fish in half if it's a large piece, add it to the saucepan and poach the fish gently for 5 minutes. It should be slightly undercooked.
Remove the fish to a plate, using a draining spoon, and strain the liquid through a sieve into a bowl.
Rinse the pan you cooked the fish in, melt the butter in it, whisk in the flour and gently cook for 2 minutes. Then gradually add the strained fish stock little by little, whisking all the time. When you have a smooth sauce turn the heat to its lowest setting and let the sauce gently cook for 5 minutes.
Meanwhile remove the skin from the white fish and divide it into chunks (quite large), and microwave the mash for half its cooking time.
To the sauce add in the crême fraiche, followed by the cornichons, parsley and dill. Give it all a good seasoning and remove it from the heat.
Gently combine the fish with the sauce then spoon it into the baking dish.
Bake on a high shelf of the oven for 35-40 minutes.