Germans take tremendous pride in their sausages, known around the world for their flavor. Many recipes for german sausage are closely guarded family secrets, while others are hotly contested for their authenticity. Some are served on a roll, as americans serve hot dogs, but others are eaten with a knife and fork, depending on how fancy the meal is. German sausage with curry ketchup, known as currywurst, is the number one street food or fast food known as imbissbuden. Vendors sell them at street fairs and carnivals, and they're a great introduction for those unfamiliar with this ubiquitous german delicacy. It starts with a grilled sausage (berliner currywurst is a pork sausage which resembles a hot dog, while other cities might use bratwurst) and curry-flavored tomato ketchup. A good currywurst is made with good-quality sausage that is grilled hot, and the ketchup should have body rather than being the thin, watered-down stuff found in squeeze bottles. Included below is a recipe for homemade ketchup that starts with tomato paste, just in case you don't have any ketchup on hand.