Toast the cumin, coriander and peppercorns in a dry pan, then leave to cool for 5 minutes.
Crush the cardamom pods in a pestle and mortar, shake out the seeds and pick out the pods. Add the toasted spices and crush with a good pinch of sea salt.
Transfer to a large bowl. Peel and finely grate in the garlic and ginger.
Cut the venison into 2cm to 4cm pieces, then add to the spices with the yoghurt. Mix everything together to coat, cover and leave to marinate.
Peel and finely slice 6 onions, and roughly slice the other 3. Finely chop the chillies.
Heat a little ghee or butter in a large saucepan on a medium-low heat and sauté the thick onion slices with the garam masala for 10 minutes, or until softened but not coloured. Spoon onto a plate and set aside.
Add a little more ghee to the pan, add the chilli and the remaining onions; cook for 5 minutes until softened.
Add the venison, with all the marinade from the bowl, and turn the heat up to high. Fry for 5 minutes.
Chop and add the tomatoes, reduce the heat to low, cover and cook for around 4 hours, stirring occasionally. After 2 to 3 hours, stir in the reserved onions and cook for another hour or so with the lid off, stirring occasionally.
To finish, pick and stir through the coriander leaves. Serve with steamed rice, extra yoghurt, naan and mango chutney.