Break the eggs into a bowl and mix until the yolks are broken, but there are still separate areas of white and yolk.

Add the dashi, sugar, soy sauce sake and potato starch to a bowl and stir to combine.

Add the oil and onions to a non-stick frying pan over medium high heat and saute the onions until soft and just starting to brown.

Push the onions to the edge of the pan and add the tonkatsu in the center.

Pour the sauce around the cutlet and cover for 1 minute to let the sauce thicken and the katsu reheat.

Remove the lid and flip the katsu over using a spatula. This ensures the katsu is well seasoned on both the top and bottom.

Pour the egg all over and around the katsu and sprinkle on the green onions. Cover and steam until the egg is just a little less cooked than you want. Personally I like my egg creamy, so I let it steam until the egg is set on the bottom but still a little runny on top. By the time it gets to the table, the residual heat cooks it to a creamy custard texture.

Put the hot rice into bowls and cover with the tonkatsu and egg mixture, drizzling any remaining sauce on top.