1. Preheat the oven to 200°C/fan180°/gas 6. Cut the squash lengthways and scoop out the seeds, then cut into 2.5-3cm thick wedges. Mix all the seed spices together to make the panch phoran.
2. Heat a dry heavy-based frying pan over a medium heat. Add the dried whole chillies and shake them around for about 30 seconds until they have darkened slightly, but take care not to let them burn. Remove and leave to cool, then grind coarsely in a spice grinder. Put the oil into a roasting tin with the ground chilli, garlic, 1 tbsp panch phoran, 1 tsp sea salt flakes and plenty of ground black pepper. Mix well.
3. Add the wedges of squash to the tin and turn them over a few times in the olive oil mixture until well coated. Turn flesh-side up and roast for 30-40 minutes until tender.