Boil the eggs until fully cooked, then peel and mash in a bowl.
Drain the tuna well and add it to the eggs.
Mash in the avocado until creamy but still slightly chunky.
Add a spoonful of Kewpie and a small amount of Dijon mustard.
Season with salt to taste.
Mix until well combined.
Toast your bread if desired, pile the mixture on generously, and close the sandwich.
