• Place the diced onion in a bowl. Add 3 Tbsp of oil and mix well. Cover and microwave for 3 minutes. Remove the cover, microwave for 1 more minute. Transfer to the refrigerator and let cool completely.
  
• In a large bowl, combine the ground beef and pork. Add the egg, milk, salt and oyster sauce, mixing until combined. The mixture will be wet. Add in the breadcrumbs and mix thoroughly. Add the cooled onions and knead the mixture well with your hands
  
• Divide the mixture into 4 equal portions. Toss each meat patty from hand to hand and shape into oval patties. Lightly indent the center of each patty so it cooks evenly.
  
• Lightly oil a large frying pan and place the patties in the pan before turning on the heat. Turn the heat to medium. As the patties begin to release fat, let them cook for about 2 minutes.
  
• Flip the patties, cook for 2 more minutes.
  
• Pour 1 ½ Tbsp water per patty into the pan, adding water both between and around the patties. Cover the pan, reduce heat to low and cook for 5 minutes. Turn off the heat and let the patties rest, covered, for 1 minute. Do not open the lid during this time.
  

Sauce

• In a separate pan over medium-low heat, melt the butter. Add in the tonkatsu sauce, sugar and minced garlic. Cook until sugar is dissolved.

To Serve

• Plate the hamburg and spoon the sauce over the hamburg. Serve with steamed rice, a sunny-side-up egg, and a simple side salad for a classic, comforting meal.