• Chop the onion finely. Heat oil in a pan over medium high heat and saute onion until translucent. Season with salt & pepper. Transfer to a bowl and cool.
• Add meats into a big bowl. Add the cooled onion, egg, milk, panko, salt, and pepper into the bowl. Mix well (mixing with your hands work best).
• Pinch off meat from the mixture into 6 parts. Toss each portion from one hand to the other about 5 times to release trapped air. Shape each piece into oval patties (not too flat). Put them in the fridge for at least 30 minutes.
• In a large pan, heat oil over medium heat and place the patties on the pan. Indent the center of each patty with 2 fingers because the centers will rise with heat.
• Flip the patty after 5 minutes or until they are browned. Once flipped, cover and cook for approximately 5 more minutes (or until cooked through).
• Remove the patties, but don't wash the pan! (You'll use it for the sauce).

Sauce

• Combine all liquid sauce ingredients in a bowl.
• In the same pan as the patties, add butter and then the sauce and mix well.
• Put heat on medium low and simmer for a few minutes until the sauce thickens (skim off any excess fat that may come up at this stage).
• Once thickened, pour over hamburg and serve!