Open the oysters, collect the juice, filter, pour with the oysters into the bowl of the mixer, add the milk, the chopped lemon balm leaves, the lemon juice, 2 pinches of salt and sugar. Chill.
Wash and prepare the sorrel leaves, keep them cool.
In a large Dutch oven, bring the vegetable broth with the water and white wine to the boil, add the skate fins, skin side down, cook gently without boiling or simmering. After 5 minutes, stop cooking.
Drain the fish wings, peel them, arrange them on the plates.
Prepare a vinaigrette with cider vinegar, salt, sugar. Emulsify with olive oil.
Season the sorrel and add it to the plates.
Remove the bowl from the blender, add the two ice cubes. Mix everything until you get a very frothy preparation.
Serve as an accompaniment to skate.
