To clean the mussels, brush each individual of them. If there is seaweed attached to it, remove it. Make sure to check if the mussel is closed. If not, discard it.
For the creamy sauce, chop 2 shallots into small sizes, and roughly chop 4 cloves of garlic. Take the leaves off from the tarragon (We will need about a quarter cup of the tarragon leaves in total, you can adjust this amount based on your preference)
Heat up a pan at medium heat, add some olive oil, and the shallot into the pan. Cook until the shallot becomes tender, and then add the garlic in. Stir well.
Add 1 cup of dry white wine to deglaze the pan. And then add 3 tbsp of butter, a cup of heavy cream, and the tarragon, mix well. Let it simmer for about 2 minutes.
Once the sauce boils, add the mussel in, mix them well with the sauce and cover with a lid. Let it simmer for about 2 minutes.
Two minutes later, open the lid and let the mussel cover with sauce. Add parsley or thyme and remove the pot from the heat, and it is done!