１Remove the heads from the prawns, then remove the shells, leaving the tails. Make a cut along the belly side to open and then remove the vein from the back. Chill them in a refrigerator. Boil the heads in salted water and also chill them in a refrigerator. ２Combine the ingredients and seasonings for the dressing in a bowl. Mix well and set aside for a while to allow all the ingredients to blend together. ３Make a bed of leaf lettuce on a dish. Lightly sprinkle salt over the prawns' bodies and heads and place them on the lettuce. Pour the dressing over the dish and top with the mint leaves.