2) Using the towel as a mitt, hold the oyster firmly on a flat surface. Insert the tip of an oyster knife between the shell halves, and work it around one side to the other as you pry it open.
3) Using the knife, cut the muscles away from the top, flat shell, bend the shell back, and discard it. Run the knife underneath the oyster to detach it completely, but leave it in its shell (take care not to cut the meat itself).
4) Nestle the oysters in a bed of crushed ice or wet rock salt to keep them steady. Garnish with lemon quarters and serve immediately with cucumber mignonette sauce and cocktail sauce.
For the cucumber mignonette sauce:
1) In a small bowl, combine the rice wine vinegar, shallot, ginger, cucumber, sugar and black pepper, mixing well with a fork.
2) Cover and chill for at least one hour or up to the day before you plan to serve, to allow the flavours to come together.
For the cocktail sauce:
1) Mix all the ingredients in a blender to combine.
2) Cover and refrigerate until ready to use.