In a large bowl, toss the butternut squash with the olive oil, cumin, coriander and cayenne and then season with salt and pepper.
Spread the butternut squash on a baking tray in a single layer and roast in the oven for about 30 minutes, until tender and lightly browned, tossing once halfway through.
Whilst butternut squash is roasting, place the potatoes in cold water, bring to the boil and turn down to simmer for 15 – 20 minutes until softened, drain and mash.
When the butternut squash is ready, remove it from the oven and transfer it to a casserole dish along with the chickpeas.
Spoon the potatoes over the top of the spiced butternut squash and chickpea mixture and use a fork to level
Place the casserole back into the oven for a further 15 – 20 minutes until the potato topping has crisped to personal preference.