What is "bitterballen"?

Bitterballen are a traditional Dutch snack food consisting of a deep-fried, savory meatball coated in a crunchy, breadcrumb exterior. They are usually served with mustard as a dipping sauce. The meatballs are usually made from a combination of beef, pork, and veal, and are usually filled with a creamy roux-based sauce. Bitterballen are typically served as an appetizer or snack, and are commonly found in pubs, bars, and cafes in the Netherlands.