Gently heat the oil in a pan then add the onion and sauté for a 2 - 3 minutes.
Stir in the green pepper and cook, stirring for 2 minutes then add the ginger and garlic paste. Stir all until combined and the pepper begins to soften.
Add the diced potatoes combining well into the mixture. Then stir in the spices, green chilli and salt for about 2 minutes. Stirring well until everything is coated with the spices.
Pour in the hot water and bring the mixture to a simmer and cook for 10 minutes until the potatoes are softened and water has reduced.
Turn off the heat, stir in the coriander and garam masala and transfer to Balti serving dishes.