Currywurst

Method

1. 1Dice the onion finely and cook it in half the oil over medium heat until soft and translucent, about 5 minutes. Keep it pale: you want its sweetness, not roast flavour.
2. 2Add the tomato paste, the sweet paprika and half the curry powder. Fry them in the fat for a minute or two, stirring, until the paste darkens and smells toasted. Sweet paprika is the German choice here, the Paprikapulver edelsüß sold in every supermarket; smoked Spanish paprika pushes the sauce towards chorizo and away from a Berlin stand.
3. 3Pour in the beef broth and the vinegar, then add the Worcestershire sauce, the sugar, the salt and the pepper, scraping everything off the base of the pan. Broth and Worcestershire carry the savoury side of this sauce, which is why fruit juice has no job here when sugar is already going in.
4. 4Simmer gently for 10 to 15 minutes, until the sauce coats the back of a spoon. Taste it and balance it: sweet, sour and spiced should all land, one after the other. Blend it smooth if you want the texture of a snack stand.
5. 5Cook the sausage while the sauce simmers. A raw bratwurst in its casing goes into barely simmering water for 10 to 12 minutes first, then gets patted dry and seared in the rest of the oil over high heat for 3 to 4 minutes until browned. That is the same poach-then-sear order used for plain bratwurst, with water standing in for the beer, since the sauce will cover whatever flavour the beer might have left. A skinless boiled sausage comes cooked already and goes straight into the hot fat for 3 to 4 minutes, until the surface browns and tightens.
6. 6Cut the sausages into bite-sized rounds. Berlin cuts a skinless sausage, and the soft pieces drink up sauce; the Ruhr keeps the casing, so every piece gives a little resistance before it breaks.
7. 7Pile the sausage into shallow bowls, spoon the hot sauce over it and dust generously with the remaining curry powder. Serve with fries under a stripe of ketchup and a stripe of mayonnaise, or with a plain roll for wiping the plate.