Combine ground pork, ground beef, sautéed onion, breadcrumbs, soy sauce, ketchup, egg, salt, and pepper in a bowl.

Mix thoroughly until the mixture becomes sticky.

Divide the mixture into four portions and shape into hamburger steaks.

Heat oil in a pan and cook the hamburger steaks until golden brown on both sides.

Reduce heat to low, add 1/3 cup water, cover, and steam until fully cooked.

Prepare the sauce by slicing mushrooms and onion into small pieces.

Melt butter in the same pan used for cooking steaks, then sauté onion and mushrooms.

Add soy sauce, sugar, ketchup, and water to the pan and simmer until thickened.

Mash boiled potatoes and mix with mayonnaise and Parmesan cheese.

Shape the potato mixture into snowman shapes and coat with Parmesan cheese.

Decorate the snowman faces with seaweed, carrot, and black sesame.