Begin by grating half of one onion finely; this will blend smoothly into the beef mixture to keep the patties moist and tender. Set the grated onion aside. Thinly slice the remaining onion and melt a tablespoon of butter in a frying pan over low to medium heat. Slowly cook the sliced onions, stirring occasionally, allowing them to soften and develop a deep golden caramel color. This process brings out their natural sweetness, resulting in luscious caramelized onions that will crown the patties. In a mixing bowl, combine the ground beef with the grated onion, salt, pepper, nutmeg, cornstarch, and water. The cornstarch and water help bind the mixture and ensure a juicy interior while nutmeg adds a warm, aromatic note. Shape the mixture into a sausage shape first, then cut it into six equal portions. Flatten each portion into round patties, about half an inch thick. Using a sharp knife, lightly score a grid pattern onto each patty’s surface — this helps them cook evenly and prevents puffing up. Heat the remaining two tablespoons of butter in a pan on high heat. Brown each side of the patties quickly until a delicious crust forms, locking in the juices. Then reduce the heat to low and continue frying each patty gently for 2 to 3 minutes to cook through without drying out. Serve the Karbonader topped generously with the silky caramelized onions. They pair wonderfully with boiled potatoes, stewed peas, and a rich brown sauce for a traditional Danish meal. For a lighter option, place the patties on a slice of bread for a tasty lunch or snack. Tip: Cooking the onions low and slow is key to achieving that perfect caramelization — don’t rush this step! Also, scoring the patties not only looks charming but helps keep them flat and cook evenly during frying.