The day before you plan to eat them, tip the potatoes into a pan of cold water and add the turmeric and pinch of salt. Bring to the boil, and simmer gently for 2-3 mins until just cooked. Drain, leave to cool, then chill overnight if you can.

Heat oven to 200°C / 180°C (fan oven) / 395°F / Gas Mark 6. Drizzle 1 tbsp of the oil in a shallow roasting tin (preferably non-stick), and place in the oven. Pour the rest of the oil into a large bowl and add the ginger, garlic, fennel seeds and cayenne pepper. Tip the cold chips into the bowl and gently toss with your fingers until evenly coated. Remove the tray from the oven and scatter over the chips. Use a spatula to coat the chips in the hot oil, then lay them out in a single layer and roast for 30 mins. Use the spatula to turn, then return to the oven for 15 mins until crisp and golden.