Tip the mince, onion, egg, breadcrumbs, nutmeg and garlic powder into a large bowl and generously season with black pepper. Mix everything together using your hands, then shape the mixture into six patties. Transfer to a plate, cover and chill for 1 hr or up to a day.

Heat a barbecue to medium or until a thin layer of coals has turned grey. Cook the burgers for 10 mins, turning occasionally, until lightly charred and cooked through. Top with sliced cheese during the final 2 mins of cooking time, if you like.

Serve the burgers in the buns topped with the lettuce, tomato and lingonberry sauce, if you like.