I made loco moco for dinner the other night but I didn't do the fattie, I just did hamburger patties. I mixed the hamburger with chopped onion and Worcestershire sauce, spog and fried them and them chopped up mushrooms and sauted them in the same pan after the meat. Then I made gravy in the same pan with the mushrooms and burger fond in there with the brown gravy mix. Costco is the place to buy that BTW. I think it was like $4 for a big spice container full. The same container at my Walmart was almost 8.
Anyways, not super traditional and not near as fancy as yours but well recieved none the less!