It's deliberately cooked with a sharp vinegar tang and a touch of sweetness from apple syrup or gingerbread, giving it a distinctive sweet-and-sour edge unusual in Dutch cooking.
Beef is marinated for days in vinegar and spices, then slow-braised with onions and thickened, sometimes with crumbled gingerbread (ontbijtkoek), until it turns dark and richly sour-sweet. Limburg market stalls and eateries ladle it over fries as a filling, tangy plate.