Boil two sliced onions in a cup of water.

Pour off this water; add another cup, and two tablespoonfuls of wine, a saltspoonful of pepper, and salt to taste (about half a teaspoonful).

Put in the fish, and cook for twenty minutes.

Thicken the gravy with a heaping teaspoonful of flour, rubbed to a cream with a teaspoonful of butter.

If wine is not used, add a sprig of chopped parsley and the juice of half a lemon.
These methods will be found sufficient for all fresh fish, no other special rules being necessary.