Peel onion, cut into fine cubes and add to the pan.
Cook onions until soft and translucent. This will take about 5 to 10 minutes.
In the meantime mix eggs, milk and salt.
Remove parsley stems and chop the leaves finely.
Add bread cubes to a large bowl.
Pour milk mixture over the bread cubes and mix well.
Add onion mixture and parsley to the bowl and mix well again.
Allow the bread mixture to rest for about 1 hour.
Bring about 1 gallon of water to a boil in a large pot.
In the meantime prepare four 2-feet long sheets of non-stick aluminum foil.
Add one quarter of the bread mixture on each sheet and roll into a log. Twist both ends of the log to close tightly. Make sure the rolls are filled well and no air pockets have build.
Set rolls into the boiling water and let simmer on medium heat for 45 min.
Remove rolls from the water, let cool to touch and remove foil.
Cut each log into ½-inch slices, brush with butter and serve.