Mince the onion and microwave it in a heatproof container covered with plastic wrap for 1 minute at 600W. Let it cool.

Combine breadcrumbs and milk in a bowl and let them soak.

Coarsely chop the steamed soybeans.

Add ground meat, chopped soybeans, onion, salt, and pepper to the breadcrumb mixture. Mix until sticky and divide into two portions.

Shape the mixture into oval patties, pressing to remove air.

Heat salad oil in a frying pan over medium heat. Cook the patties until browned on both sides. Cover and cook on low heat for 7 minutes until fully cooked.

In the same pan, add sake, ketchup, and Worcestershire sauce. Simmer over medium heat and stir in butter until melted.