Heat 2 tablespoons of the oil in a wide shallow frying pan over a medium heat. Add the potato pieces and fry them for 6-8 minutes, turning them every now and then until they are golden brown all over. Using a slotted spoon, lift out onto a plate.
Add another tablespoon of oil and the paneer and fry for 3-4 minutes until these too are golden all over. Set aside with the potatoes.
Add another tablespoon of oil to the pan, add the curry leaves and cumin seeds and allow them to sizzle for a few seconds. Add the onions, garlic and ginger and fry gently for 5 minutes until the onions are soft and just beginning to brown.
Add the turmeric, chillies and chopped tomatoes and fry until the tomatoes have broken down to form a sauce.
Add the potatoes, 100ml water and 1 teaspoon salt, cover and simmer for 5 minutes until the potatoes are tender and the liquid has reduced to a thickish sauce.
Add the pieces of fried paneer, garam masala and peas, and simmer for 2 minutes or until the peas are just tender. Stir in the ghee and serve.