Steps

1. Finely mince 1/2 onion. (Key Tip!) Finely mincing the onion helps it blend better with the meat mixture. If the pieces are too large, the onion may fall out while cooking, so it's recommended to chop it as finely as possible.
   🕒 01:46
2. Place the minced onion in a microwave-safe bowl, cover with plastic wrap, and microwave on 600W for 1 minute.
   🕒 02:08
3. After microwaving, remove the plastic wrap, spread out the onion to let it cool, and allow it to cool completely.
   🕒 02:25
4. In a separate bowl, combine 4 tbsp panko breadcrumbs and 3 tbsp milk, and let the breadcrumbs soak.
   🕒 02:42
5. Add 250g ground pork and beef mix to a bowl, add salt and pepper (to taste), and knead until sticky and well combined.
   🕒 02:57
6. Add 1 egg, 1/2 tbsp mayonnaise, and the soaked panko breadcrumbs to the kneaded ground meat. Knead thoroughly until everything is well mixed.
   🕒 03:17
7. Add the cooled onion to the meat mixture and gently mix everything together.
   🕒 03:31
8. Divide the meat mixture into 3 equal portions. Take one portion and flatten it well, removing air. (Key Tip!) If you don't remove the air at this stage, the shape may collapse.
   🕒 03:42
9. Place 3 slices of melting sliced cheese, folded twice, in the center of the flattened meat mixture. Cover the cheese with the meat mixture so it doesn't leak out, then reshape, removing air again. (Key Tip!) Air trapped inside can cause the hamburger to crack while cooking, so make sure to remove it thoroughly.
   🕒 04:01
10. Heat a suitable amount of vegetable oil in a frying pan over medium heat for about 30 seconds.
    🕒 04:45
11. Place the shaped hamburger steaks in the heated frying pan and gently indent the center. (Key Tip!) Indenting the center before cooking helps to ensure the inside is cooked through.
    🕒 05:04
12. Sear both sides over medium heat for about 1.5 minutes each until browned.
    🕒 05:19
13. Reduce heat to low, add 1.5 to 2 tbsp water (not listed in ingredients), cover with a lid, and steam for 8 minutes.
    🕒 05:53
14. After 8 minutes, remove the lid and insert a bamboo skewer. If the juices run clear, it's cooked through. Turn off the heat, remove the hamburger steaks, and place them on a plate. (Key Tip!) If the juices are still red, cook for a little longer.
    🕒 06:08
15. Return the frying pan used for the hamburger steaks to medium heat. Add 2 tbsp ketchup, 2 tbsp Worcestershire sauce, and 1.5 tbsp mirin (sweet rice wine). Stir and bring to a boil.
    🕒 06:33
16. After boiling, heat for about 30 seconds to cook off the alcohol from the mirin.
    🕒 06:51
17. Turn off the heat and add 5g salted butter, stirring until melted. (Key Tip!) Adding the butter at the end is recommended to preserve its flavor.
    🕒 06:59
18. Pour the sauce over the hamburger steaks and serve. Enjoy!
    🕒 07:15