Russian Boiled Fish

Clean and season a whole fish and let boil with 1 sliced onion, 1/2 cup of vinegar, a few slices of lemon and 2 sprigs of parsley. Add a tablespoonful of butter and let cook until tender. Remove the fish to a platter; mix the sauce with 1 tablespoonful of brown sugar, a pinch of ginger, cinnamon and nutmeg and the juice of a lemon.
Let boil well; then thicken with the yolks of 2 beaten eggs and pour over the fish. Serve cold. Garnish with lemon−slices and olives.