Currywurst with sticky-onion oven fries

Method

1. To make the sauce, put a small pan over a medium heat. Add the curry powder, cook for 10 seconds, then pour in the ketchup, vinegar, Worcestershire sauce (if using) and sugar. Add a splash of water to loosen the sauce slightly, then bring to a simmer and cook for 2 minutes, stirring occasionally. Set aside.
2. Put a large lidded pan over a low-medium heat and add the butter and 1 tbsp of the oil. Once the butter has melted, add the onions with a pinch of salt and 1 tbsp water. Stir to coat the onions in the oil and butter, then cover and leave to steam for 10 minutes, stirring occasionally.
3. Remove the lid, then add the sugar and thyme leaves to the onions. Cook gently for 30 minutes, stirring regularly, until deeply caramelised and sticky.
4. Meanwhile, heat the oven to 180°C fan/gas 6. Peel and cut the potatoes into chips (roughly 1cm thick), then give them a good wash in cold running water to remove the starch. Dry well, then toss with the remaining vegetable oil and the cornflour. Arrange in a single layer on a baking tray (or 2), then put in the oven to cook for 20 minutes.
5. After 20 minutes, put the bratwurst in a baking dish and put them in the oven. Turn the chips over, then cook them (and the sausages) for 25-30 minutes until golden and crisp.
6. Once the onions have broken down into a sweet sticky tangle, increase the heat and pour in the beer. Simmer vigorously until the liquid has reduced almost completely and the onions have returned to a dark sticky mass.
7. To serve, divide the chips among serving dishes and dollop the sticky onions on top. Slice the bratwurst into bite-size chunks, arrange on top or alongside, then serve with the spicy-tangy currywurst sauce