Cook the rice according to your rice cooker instructions or cook in a pot. *2
Prepare the prawns by peeling off the shell, removing the tail, and cleaning out the inside.
Put all the batter ingredients into small bowl and stir until it's just mixed and refrigerated until just before deep frying.
Heat some oil to 180c(356F).
Take the batter bowl out of the fridge.
Dip the prawns into the batter then deep fry them all for just a couple of minutes (be careful not to overcook).
Place a sheet of cling wrap into a rice bowl and put some rice (1/8 of the amount of rice) into the bowl.
Make a small well in the centre of the rice and place 1 prawn into the centre.
Fold the cling wrap together and shape the rice into a triangle around the prawn.
Slightly grill the seaweed sheets and cut each sheet into 4 long strips.
Remove the cling wrap and put one seaweed strip around the rice.
Repeat for the remaining rice and prawns.
*1 If you are unable to get store bought tsuyu, add 1tsp of soy sauce, sake and mirin instead.*2 Japanese 1 cup = 180mil. And cooking rice is not included in the cooking time.*3 If you are unable to get Japanese mayonnaise, omit to add Japanese mayonnaise.