Cut the stems off the broccoli and set the florets to one side. Slice the stems into thin slices. Boil the vinegar with the water, the sugar, salt and half the ginger. Place the slices of broccoli stem in it and boil for 1 minute. Allow to cool. Preheat the deep-fryer. Brown the sesame seeds in a dry frying pan and allow to cool. Stir the sesame oil into the mayonnaise and mix in the sesame seeds and roasted garlic. Add the soy sauce to taste. Heat the wok and stir-fry half the florets. Add the garlic and ginger and season with pepper and soy sauce. Mix the tempura with plenty of sparkling mineral water to make a smooth paste. Cover the remaining half of the florets in batter and deep-fry them until they are golden-brown. Assemble the dish on a plate. Arrange the sesame mayonnaise with it. Sprinkle the sesame seeds and drizzle some soy sauce over it. Garnish with the mizuna.