Heat the oil in a deep frying pan over a medium heat. Add the onion and a pinch of salt, and cook for 8-10 mins until the onion is beginning to soften. Stir in the sugar, curry powder, paprika and onion powder and cook for 3-4 mins, until fragrant.

Pour in the balsamic, passata, apple juice and stock, then add the mustard, Worcestershire sauce and ketchup. Bring to a simmer and cook for 15-20 mins until bubbling and reduced. Add the bicarbonate of soda and let it bubble, then stir in well. Season to taste and blitz the sauce using a hand blender or spoon into a blender.

Meanwhile, cook the bratwurst according to pack instructions then thickly slice and arrange on a serving platter. Spoon the sauce over the top to serve.