Preheat the oven to 200°C/fan180°C/gas 6. Season the chicken's cavity with salt and pepper and place in a large roasting tin. Cut one orange half into wedges and place some inside the cavity and some around the chicken. Place the onion wedges and the bay leaves in the chicken cavity. Tie the legs together with string. Rub all over with the olive oil, season and scatter with garam masala. Squeeze the other orange half into the bottom of the roasting tin, add 150ml hot water, cover with foil and roast for 45 minutes.
Meanwhile, toss the red onion wedges and squash with the sunflower oil and then scatter with the ginger, spices and garlic and mix together well so it is all coated in the spicy mix. Tip into a very large roasting tin (large enough so the vegetables can sit happily in one layer without being piled up so that it roasts evenly and doesn't stew). Place in the oven and roast for 40-45 minutes or until tender and lightly browned around the edges.
Remove the foil from the chicken and roast for a further 20-30 minutes or until the skin is golden and the juices from the thigh run clear when pierced with a skewer.
For the raita, mix the yogurt with the chopped mint and lime zest and place in a small serving bowl.
Serve the chicken sliced with the roasted squash and the mint raita on the side and pour the chicken roasting juices over the top as an instant gravy.
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