1 tablespoon of mustard oil.
1 teaspoon of rice wine vinegar.
1 teaspoon of mustard.
½ teaspoon of salt.
½ teaspoon of wasabi.
½ cup of crayfish tails.
With a fork, mash the boiled potatoes with a fork.
Add the mustard oil, vinegar, mustard, salt and wasabi.
Set aside and allow to cool.
Roll out the potatoes into appropriately sized pieces; placing a craytish tail on top of each piece.
Serve warm.
Source: http://www.sushirecipes.org/crayfish-sushi.html