To make my Donburi Sauce: I bring a mixture of: kikkoman mirin brown sugar and H20 or chicken stock (in lieu of Dashi or japanese soup stock) to a simmer. ***Adjust saltiness/sweetness by adding a few more soy sauce/sugar/stock*** Then, I add sliced white onions and green onions and let it simmer for a few minutes. In the last few minutes, I add sliced green onions to the simmering sauce and let it simmer a wee bit further. Super easy, i swear.
To prepare the Katsudon: I first dredge my pork cutlets/chops in flour, dip in beaten eggs and finally dredge in panko/japanese bread crumbs. Then I deep-fry until golden. Once
cooked, I place the tonkatsu in the simmering savory sweet sauce and
pour some beaten eggs on top and let simmer for a few mins until the
egg is just set. Sprinkle a few more scallions or green onions on top and serve with steamed rice. (Optional: Serve with raw egg)