In a large saucepan, put in the oil, onion, shallot and garlic cook over a medium low heat, just until they are slightly soft.
Add in the chopped herbs, Pernod if being used and mix in the onion mixture.
Add the mussels into the pan and cover with the white wine, bring slowly to a boil, stirring occasionally.
Continue cooking until the mussels have opened, this takes between 2 and 5 minutes.
Discard any mussels that did nit open.
Add the creme fraiche if using and cover until ready to serve with the frites.