Tonkatsu sauce (Japanese style Worcestershire sauce or steak sauce)
Put eggs, flour, natto and its accompanying dressing/mustard packet contents in a bowl. Don't mix it yet.
While heating a pan, add finely chopped cabbage to the bowl, and mix it up into a ball.
Pour the mixture into the heated pan, and top with bonito flakes and tempura crumbs to taste.
Flip over, press down with a spatula to shape, and cook on both sides.
After cooking, top with as much Japanese-style Worcestershire sauce, mayonnaise, and aonori as you like, and enjoy.
Story Behind this Recipe
My family loves natto and goes through it like there's no tomorrow... Occasionally, a package of forgotten natto makes an appearance from the back of the fridge, This is what I always make during times like these.
The water content from the roughly chopped cabbage will help shape the mixture, so mix after adding all of it to the bowl. If it is still too thick after flipping it over and pressing down on it a bit with a spatula, cover it with a lid, and steam-cook it for a bit.