Rinse the mussels under running water. It is better to throw away open and damaged shells.
Bring the water to a boil in a large saucepan. Put the mussels in a saucepan, cover and cook for 5-6 minutes.
The mussels are ready (they should open up, and not discard the opened ones), we choose a slotted spoon. Remove from the shells and remove the algae.
Cut the onion into half rings and fry in butter.
Add the mussels, fry for 5 minutes, stirring, so that the mussels are soaked in butter. Sprinkle the finished mussels with parsley and serve to the table.
