Wash the mussels thoroughly with warm water and sea salt. Place them in a deep pot and pour in fresh water to cover the mussels totally.
Add 1 bag of fennel tea, whole garlic heard which you cut just slightly to release the aroma. Add rosemary.
Boil the mussels for 10-15 minutes or until they all open. (if any of them doesn't open, throw it away.
Remove the mussels from the water and place them in a deep plate or a bowl. Add butter and let it melt. You can add some of the water where they have been boiled to help the butter melt quicker. Add lemon juice and enjoy!