Put Panko in a large bowl, add milk and stir. Add meat, raw egg, salt, and pepper to the Panko mixture, and mix very well. Divide the meat into 2 pieces and roll into oval balls. Push down to form flat patties.
Heat oil in a frying pan at medium heat. Place the patties in the hot oil, and fry for 4-5 minutes on one side. Flip over and fry for 3-4 minutes covered, until cooked through. Do not wash the frying pan yet.
Make Loco Moco sauce. Put butter in the same pan used for cooking the steaks and melt at medium heat. Add flour and stir constantly, cooking for 2 minutes. Slowly add beef broth. Use a whisk if needed. Add ketchup and Worcestershire sauce. Add salt and pepper to taste.
Plate steamed rice, lettuce, and tomato. On top of the rice, place a steak, sauce, and a sunny-side-up egg. Assemble another one.