Mince the onion and place it in a microwave-safe container. Add 1 tsp salad oil and microwave at 600W for 1 minute. Let it cool.

In a bowl, combine milk and breadcrumbs, letting them soak.

Add ground beef and pork mix, minced onion, salt, pepper, and nutmeg to the bowl. Mix until sticky.

Divide the mixture into two portions and shape into oval patties, removing air pockets.

Heat 1/2 tbsp salad oil in a frying pan over medium heat. Add patties and cook until browned.

Flip the patties and cook until browned on the other side. Cover with a lid and cook on low heat for 7 minutes to ensure they are cooked through.

Remove patties from the pan. Add sake, ketchup, and Worcestershire sauce to the pan and simmer over medium heat.

Add butter to the sauce and stir until melted.