To make the dukkah, preheat the oven to gas 4, 180ºC, fan 160ºC. Roast the hazelnuts and sesame seeds separately until golden.
Meanwhile, toast the cumin and coriander seeds in a dry pan for 1 minute until fragrant. Allow them all to cool, then whizz in a blender or crush with a mortar and pestle along with the paprika, 1tsp of sea salt and a pinch of black pepper.
Preheat the oven to gas 7, 220ºC, fan 200ºC. Put the oil in a roasting tin and heat in the oven. Cut the parsnips lengthways and in quarters, then carefully place them in the hot oil. Season to taste and turn to coat. Roast for 30-45 minutes (turning halfway) until golden and tender. Remove and toss in the dukkah while hot.