If you are using leftover chicken katsu that's already been fried, you can proceed to step 3. Otherwise, go follow the instructions here for preparing and breading the chicken cutlets and come back to step 2 to fry it.

Preheat 1 ½-inches of oil to 355 degrees F (180 C). Fry the chicken, flipping it over at least once until the breading is golden brown (about 4-5 minutes). Transfer the katsu to a paper towel-lined rack and let it cool enough to handle.

Cut the chicken katsu into ¾-inch slices. Break the eggs into a bowl and lightly beat them.

Slice the onion thinly and add it to an 8-inch non-stick omelet pan, along with the dashi, sake, soy sauce, and sugar.

Bring the onion mixture to a simmer and cook them until they are tender.

Add the sliced cutlets and let them cook until they've soaked up the sauce on one side.

Flip the chicken over and continue cooking until they're warmed through and fully cooked.

Drizzle the beaten egg evenly over everything.

Gently mix the egg with tongs or chopsticks, ensuring it flows between each piece of chicken and then slam the pan against the stove (don't do this if you have a glass-topped stove) to help redistribute the uncooked egg.

Turn off the heat and allow the residual heat to cook the egg until it starts to turn opaque, but is still creamy. If you want your eggs more thoroughly cooked, you can cover the pan with a lid before turning off the heat and let it steam.

Serve over a bed of hot rice and garnish with mitsuba or scallions.