Put the mussels in salted water for a bit before you begin cooking them.
After they've sat in it, wash them and clean them under running water with a wire brush, while also debearding them.
If there are any opened mussels, throw them out.
Mix all of the remaining ingredients with the mussels in a wide pot.
Cook with a lid on for about 20 min. on a low stove, while stirring often. This should be enough time for the mussels to open up.