I basically did the same thing I normally do for oyakodon except with katsu, so I don't have a specific recipe recommendation.
Here's what I did though:
Frying the katsu
-panko bread crumbs
Score the pork with a knife on both sides (and cut apart any stringy fatty sections to make it easier to chew), season it with salt. Coat it in flour, then dip it in the egg and finally coat it in panko. Deep fry on low-medium heat (like 350 degrees F? something like that) until golden brown (I think 3-5 min on each side depending on thickness), take them out and let some of the oil drain off.
-1/2 cup dashi (or if you're lazy like me, just use water and throw in a tablespoon or so of dashi powder)
-1/2 an onion, sliced
-1 tbsp sake
-1 tbsp mirin
-1-2 tbsp soy sauce (or really however much you feel is appropriate)
-1 tbsp sugar
- (Japanese) parsley
Very lightly beat the egg with chopsticks and break up the membrane a little bit. Mix dashi, sake, mirin, sugar and soy sauce in a small flat pan (it helps if the edges are at an angle and not vertical but it's not hugely important) and add the onion. Cover with a lid and simmer until the onion is cooked, then cut the katsu into slices and add on top and pour the egg onto it, cover on high heat for like 30s and then remove from heat. Top with parsley and then slide the whole thing onto rice (this is where the type of pan helps a bit).