Heat the oven to 200°C/Fan 180°C/Gas 6. Cut the quinces in half with a sharp knife. Cut a circle around the core and pips. Take care to remove as little flesh as possible. Scoop out the middle with a teaspoon.
Place the quinces flesh-side down in an ovenproof dish. Pour in 200ml cold water. Slide into the oven and cook for 40 mins. Tip the rice into a bowl and cover with cold water. Whisk with a fork till the water turns cloudy (this is the starch). Drain.
Tip the rice into a small pan. Pour in 350 ml boiling water. Add a pinch of salt. Cover. Bring to the boil. Turn the heat right down. Gently simmer for 8 mins till the water is absorbed and the rice is tender. Take off the heat. Set aside, lid on, for 5 mins to finish cooking the rice.
Meanwhile, peel and finely chop the onion. Halve the chilli and flick out most of the seeds. Keep a few in for a little heat. Finely chop. Finely chop the mint leaves.
Halve the pomegranate around its middle. Hold one half in your hand, cut-side down. Whack with a wooden spoon over a bowl. The seeds should tumble out. Repeat with the other half. Set aside for later.
Heat a large frying pan over a medium heat. Tip in the pine nuts. Toast for 2-3 mins, shaking the pan, till golden and nutty smelling. Tip into a bowl and set aside.
Set the pan back on the heat. Add ½ tbsp oil. Add in the onion and chilli. Fry for 3 mins till just softened. Add the venison and 1 tsp mixed spice. Cook for 5 mins till browned. Add the toasted pine nuts and most of the mint. Season to taste.
Roughly chop the spinach and stir through the rice to wilt it slightly. Stir in half of the pomegranate seeds. Set the quinces on a plate and pile on the spiced venison. Serve with the spinach rice. Scatter over the remaining pomegranate seeds and mint.