1. Cut potatoes into 2 cm cubes.
2. Heat mustard seeds in a large pan until they start to pop.
3. Add ghee, onion, garlic and ginger; cook, stirring, until soft.
4. Add turmeric, salt, pepper, chilli, cumin, garam masala and potato.
5. Stir until potatoes are coated.
6. Add water; simmer, covered, 15-20 minutes, or until potato is just tender; stir occasionally.
7. Add peas, stir; simmer, covered, 3-5 minutes, or until potato is cooked and liquid is absorbed.
8. Stir in mint.
9. Garnish with parsley if desired.