In a bowl, whisk together the coconut milk and chickpea flour. Set aside.
In a pan, heat oil and add cumin and mustard seeds. Once the seeds start popping (about 30 seconds), add the onion, followed by the ginger and garlic.
Sauté until the onions become soft (about 5 mins). Deglaze with water as needed.
Add the salt, crushed chilli flakes, turmeric, and black pepper. Allow the spices to toast for about a minute.
Add the potato and stir to coat with the spices, then cook for 5-7 mins. Adding water as needed to keep things moving.
Add the coconut milk mixture and water.
Reduce the heat to a simmer and allow to cook until potatoes are fork tender, stirring occasionally.
Add Kasuri methi if using, followed by lemon juice, and stir to combine.
Adjust salt and chilli flakes to taste.
Garnish with cilantro