Dice the onion, celery, eggplant, and garlic into small cubes, sauté them, then roughly blend in a blender and let it cool down.
Add the minced Hanwoo brisket, minced Hanwoo chuck eye roll, bread crumbs, egg, salt, and pepper to the mixture from step ①, and knead it into round patties.
Place the patties from step ② in a 220°C heated oven and cook until about two-thirds done, then top the steak with a slice of Provolone cheese (feel free to add 2–3 slices to your preference).
Serve the finished Hamburger steak on a plate with rice, a fried egg cooked on one side, and steak sauce.
In a pan with oil, sauté the chopped onion until it turns a brown, then add the sliced button mushrooms and sauté a few more minutes.
Once sautéed, add water, sugar, butter, ketchup, dark soy sauce, and white pepper, and bring to a boil until the sauce thickens.