PREHEAT OVEN TO 325F. Remove and discard the crust from the bread.
Tear the bread into pieces and set aside.
Melt the butter in a skillet over medium heat on the stove, add the onions and cook, stirring for 5 minutes or until softened.
Add the wine, bring to a boil and cook 1 minute. Add the bread and cook, stirring 5 minutes.
Scrape the mixture into a mixing bowl. Roughly cut the whitefish and salmon into 1-inch pieces and add to the bread in the mixing bowl.
Add the salt, pepper, coriander and nutmeg and mix.
Place the mixture in a food processor and process until smooth.
Or, fit a meat grinder with a medium die and grind the fish mixture twice. Transfer mixture to a mixing bowl and place bowl over a pan of ice water.
Add the eggs and the whites and mix well. Slowly add the cream.
Pack the mixture into a 9-by-5-by-3-inch glass, ceramic or metal loaf pan. Tap the pan on a counter to firmly pack.
Cover tightly with a double layer of aluminum foil. Place loaf pan in a larger pan and fill with boiling water until it rises halfway to the top of the loaf pan.
Place in the oven for 1 hour. Remove pate from oven and its water bath. Place loaf pan on a baking sheet.
Cool for 1 hour. Refrigerate for at least 3 hours.
To remove, run a knife around edges of the pate. Dip loaf pan in hot water for a minute. Turn out onto a plate. Serve with toast or crackers.