For Tempura Batter: Whisk together ingredients. Can be used for up to 1 hour. Keep cold!
For Crabs: Heat 1/4-inch of corn or peanut oil in a heavy skillet until very hot but not smoking. Fry the crabs in batches for about 2 minutes on the first side, then turn and fry for another minute. The crust should be golden. Be prepared the crabs will split when you fry them; a splatter screen will come in handy.
Drain on paper towels and serve with dipping sauces.
For Balsamic Syrup: Put all ingredients together and reduce over medium heat, down to 1/4 of its liquid. Strain and discard onion.
For Red Pepper Syrup: Combine all ingredients in a saucepan. Reduce down to 3/4 of a cup. Thicken with the arrowroot.
For Wasabi Cream: Dissolve Wasabi in water. Whisk in creme fraiche and lemon juice. Season with salt.