Start by boiling the eggs for 9 minutes, once done place into an ice bath. Carefully peel the eggs, and set 2 aside.

Finely chop the remaining four eggs and place into a mixing bowl, you can also mash with a fork if you prefer a finer texture. Add the Ponzu and Mayonnaise, stir well and then season to taste with salt and black pepper. 

To assemble, remove any crust from the shokupan, then lay on a tray. Lightly butter each piece of bread, spoon the egg mixture evenly between the two slices. Create a small divot in the egg mixture and place one of the whole eggs in the middle. 

Place the other slice on top and press down gently. Cut lengthways and repeat for the other sando. Dip into Miso Hot Sauce for an added buzz.