Wash the new potatoes the cut in half, with the bigger ones you may need to cut into 1/3 or 1/4. Keep the skin on as I think it tastes much better.
Into a medium size saucepan add the oil and heat, after about 30 seconds or so add the mustard seeds and cumin seeds. Allow both seeds to sizzle and the mustard seeds might start to pop a little.
Add the potatoes to the pan and toss until the potatoes are slightly coated with the oil and seeds.
Add the chilli, turmeric, ground coriander, ground cumin and salt to the pan. Then pour in 400ml of water and stir well. Bring to a boil and allow to simmer covered for about 10 minutes. Add the tomato passata or chopped tomatoes, recover and cooked for a further 10 minutes.
Once the potatoes are tender add the tomato puree and lemon juice.
Stir well, allow to cook for a further minute and its ready.
Enjoy with chapati, naan, rice or with anything you would like.