Prepare grated vegetables: Peel and grate the onions and tomatoes. Remove tomato skin before grating. Grate ginger and garlic. Chop green chillies.
Heat mustard oil and roast whole spices: Heat mustard oil in a pan on medium heat. Add cinnamon stick, cumin seeds, cloves, green cardamoms, and black cardamoms. Roast until aromatic but do not burn.
Fry onions: Add grated onions to the pan and fry on medium heat for 6-7 minutes until softened but not browned.
Add ginger, garlic, and green chillies: Add grated ginger, garlic, and chopped green chillies. Fry for 2-3 minutes until fragrant.
Cook tomatoes: Add grated tomatoes and roast on medium heat for 5-6 minutes until the tomatoes are well cooked and oil starts to separate.
Add dry spices and water: Reduce heat to low. Add salt to taste, red chili powder, turmeric powder, and Kashmiri red chili powder. Add half a cup of hot water to prevent spices from burning.
Cook spice mixture: Cook the mixture on low heat for 6-7 minutes, adding more hot water as needed, until the spices release oil and the mixture thickens.
Add boiled potatoes: Add the boiled potato pakoras pieces to the spice mixture and roast for 4-5 minutes to coat them well.
Simmer with water: Add about three glasses (approx. 3 cups) of hot water, mix well, cover, and cook on medium heat for 15-20 minutes until vegetables are fully cooked and the gravy is neither too thin nor too thick.
Finish and garnish: Turn off the heat, garnish with chopped fresh coriander leaves, and serve hot with rice or roti.