Melt the butter in a pan and skim off the white foam so you get clarified butter
Pour the calvados into a mussel pan and add the mussels as soon as the liquor begins to steam
Cook the clams until all the shells are open. Shake the pan in between so that the heat is evenly distributed.
Allow the mussels to cool briefly, then remove them from the shells
Turn the heat low and stir everything well, then stir in the parsley
Divide the mussels among the jars and pour the clarified butter over them
Let them cool or refrigerate until the butter has come to room temperature
The original dish can be found in My French Kitchen by Rachel Khoo"