This is a good recipe for a hot, poached fish with vegetables.

Ingredients:

1 salmon or sea trout 3 lb.
1 medium large onion, sliced
2 young carrots, sliced
1/2 bayleaf
Sprig of  Fennel or Tarragon
1/2 lb. Mushrooms or green Beans simmered in butter and lemon juice
1/4 bottle dry white Wine or Cider
1/4 pint fish Stock 
Salt and white Pepper
1/4 pint double Cream
1 oz. Butter, diced, worked into I oz. Flour .

Prepare the onion and carrots and put in the bottom of a large long dish.  Put the fish on top, add herbs, seasonings and stock.  Cover and cook at 400 degrees F, 200 degrees C, gas 6 for 35-40 minutes, basting occasionally with the stock. When cooked, lift fish onto a warm serving dish and keep warm.  Strain off liquid and reduce until half.  Add the cream and the wine and simmer.  Work the flour into the butter and add a little at a time, stirring well after each addition.  Pull to side of heat.
Cook mushrooms or beans very lightly, toss the fish and arrange the mushrooms or beans along the middle and in little heaps at the side.  Finish the sauce by adding a few little pieces of diced butter, let it melt, but do not boil.  Taste for seasoning, then pour over the fish and serve.