You will need
4 sliced lightly sauteed, button mushrooms
Pre-season the fish with Fish Spice or Lemon & Black Pepper Seasoning. Wrap in baking paper and put in the fridge with an ice brick on top.
Leave for 3 hours or overnight. This firms and flavours the fish perfectly.
Make the sauce first before pan-frying the fish in butter-oil mixture.
Do not overcook the fish and always cook meaty side first.
Melt the butter over medium heat. Add the grated onion and mushrooms and sauté slowly until soft.
Add the wine, turn the heat up and boil fast until almost reduced out.
Mix the White Sauce Powder with 2 T (30 ml) of the measured water and stir to form a slurry. Keep on one side.
Add the remaining water, the Fish Stock sachets and the White Sauce slurry. Bring to boil while stirring for 1 minute. Liquidise until completely smooth or rub through a sieve.
Add the cream. Taste for seasoning and finish with a small squeeze of lemon juice and a knob of butter.
Dish up the fish on warmed plates, best side up.
Coat with a generous helping of sauce and garnish with sauteed mushroom slices and watercress.