1. Preheat your oven to 200°C/Fan 180°C/Gas 6. Halve the butternut squash and scoop out the seeds (no need to peel it, though you can if you prefer). Chop the squash into small pieces and tumble them into a roasting tin. Toss with 1 tbsp olive oil and a pinch of salt and pepper, then slide the squash into the oven to roast for 35 mins, till tender.
2. While the squash roasts, make the curry paste. Peel and finely chop or grate the garlic and ginger. Halve the chilli, scraping out the seeds and pith if you prefer less heat, and finely chop it. Separate the coriander leaves from the stalks. Finely chop the stalks and set the leaves to one side. Pop the garlic, ginger, chilli and coriander stalks into a bowl. Add 2 tbsp tikka masala spice blend and 1 tbsp olive oil and stir to make a paste.
3. Peel the onions and thinly slice them. Cut the tomatoes into small pieces.
4. Warm 1 tbsp olive oil in a large pan on a high heat. Add the onions and cook for 2-3 mins, stirring frequently, till golden brown at the edges. Turn the heat down to medium and add the curry paste and a pinch of salt and pepper. Sizzle together for 2 mins.
5. Add the tomatoes and 100ml boiling water to the pan and stir well, scraping up any bits caught on the bottom. Let the mixture come to a simmer, then turn the heat down again to medium-low. Partly cover the pan with a lid and cook for 20 mins.
6. Meanwhile, rinse the rice under cold water and tip it into a small pan. Add 300ml boiling water and a pinch of salt. Cover with a lid, bring to the boil and then turn the heat right down. Gently cook for 8 mins, till all the water is absorbed and the rice is tender. Take the pan off the heat and let it sit, lid on, for 10 mins to finish cooking the rice.
7. When the curry sauce has cooked for 20 mins, add the baby leaf spinach and the double cream, stirring to wilt the leaves. The squash should be roasted by now. Fold the squash through the sauce, mashing a few pieces with the back of a spoon to thicken the sauce.
8. Heap the rice onto a couple of plates and top with the squash curry. Garnish with the coriander leaves to serve.