Clean and purge the oysters. To purge the sand from them, soak the oysters in heavily salted water in the refrigerator for about two hours.
Dice the shallot finely and add to a small bowl.
Top with a few cranks of freshly ground pepper and add the prosecco vinegar.
Stir the mignonette and allow the flavors to meld for a few minutes before serving.
Shuck the oysters and set them on top of ice or a bed of salt. Serve with the prosecco mignonette, some lemon wedges, and horseradish for topping.
Enjoy!