Cut the bread into small cubes. Add to a bowl.
In a frying pan, melt butter. Cook onions in the butter until transparent.
Add onions to the bread cubes. Combine egg yolks, milk, parsley, and seasonings. Pour this over the bread cubes. Mix this together and allow the mixture to sit for 20 minutes.
Beat egg whites until soft peaks form. Fold this into the bread mixture.
You will need a clean dish towel or a large piece of aluminum foil. Spread butter over the towel and place bread mixture over butter. Roll the towel up so that the bread mixture forms a log. Roll up ends so that they won't open.
In a large cooking pot, bring salt water to a boil. Gently place the log into the water. Cook for 25-30 minutes. Remove the log from the water and briefly rinse with cold water. Very gently remove the towel or foil. Slice the log into equal sized portions. Serve dumplings immediately.