Heat the mustard oil in a pan over medium heat. Add the chopped onions and cook until golden brown, about 5-7 minutes.

Stir in the minced garlic and ginger paste, and sauté for another minute until fragrant.

Add the halved potatoes and toss to coat in the oil and onions. Cook for 5-7 minutes, stirring occasionally, until their edges begin to colour.

Sprinkle in the cumin, coriander, turmeric, and red chilli powder (if using). Mix thoroughly to coat the potatoes in the spices.

Pour in 1 cup of water, bring to a boil, then reduce the heat to low. Cover and simmer for 15-20 minutes, or until the potatoes are tender and the sauce has thickened.

Adjust salt to taste. Remove from heat, garnish with chopped cilantro, and serve hot with luchi.