Prepare all ingredients: chop the onion, ensure ground beef is at room temperature, and preheat the skillet.

Mix ground beef, chopped onion, breadcrumbs, eggs, and mustard in a mixing bowl. Season generously with salt and pepper.

Shape the mixture into round, flat patties about one inch thick, ensuring uniform size.

Heat cooking oil in the skillet and cook patties for 5-7 minutes on each side until golden brown.

Drain excess oil by transferring cooked patties to a paper towel-lined plate.

Serve warm, paired with mashed potatoes or sauerkraut.