In a medium sauté pan over medium heat, add a splash of olive oil. Sauté the finely diced onion and minced garlic for about 4-5 minutes until the onions are translucent and fragrant.

In a large mixing bowl, combine the ground beef, ground pork, sautéed onions, garlic, panko breadcrumbs, milk, egg, chopped parsley, salt, and soy sauce. Mix thoroughly until the mixture becomes sticky and cohesive.

Divide the meat mixture into 6-8 equal portions, then shape each portion into a patty, making a slight indentation in the center of each one.

Heat a frying pan over medium heat and drizzle in some olive oil. Once hot, carefully place the patties into the pan. Cook for 8-12 minutes, flipping them halfway through until they are fully cooked.

In the same pan where the patties were cooked, add the sake to deglaze. Once the alcohol has evaporated, stir in Worcestershire sauce, ketchup, and water; mix well. Allow the sauce to simmer for about 1 minute.

Plate the hot Japanese Hamburg Steaks and generously drizzle them with the tangy sauce. Serve with steamed rice and vegetables.