Start by heating your pan over medium heat and add the oil. Once shimmering, add cumin seeds and toast them for about 30 seconds until fragrant, releasing a nutty aroma.
Add the finely chopped leeks to the pan and cook gently, stirring occasionally. Let them soften over about 8 minutes until they become translucent and sweet-smelling, with a slight golden hue.
Stir in the diced potatoes, ensuring they are coated with the leek mixture. Cook for another 5 minutes, allowing the potatoes to absorb flavors and develop a light crust on some edges.
Add the ground spices: coriander powder, turmeric, and the remaining cumin seeds if using whole. Toast the spices for about 1 minute, stirring constantly, until fragrant and slightly darker.
Pour in the coconut milk and stir well to combine everything into a creamy sauce. Bring the mixture to a gentle simmer, then reduce heat to low and cover partially.
Let the curry simmer gently for 15-20 minutes, stirring occasionally, until the potatoes are tender and the sauce has thickened slightly, coating the ingredients with a velvety finish.
Taste the curry and add a squeeze of lemon or lime juice for brightness. Adjust salt if needed, and cook for another 2 minutes uncovered if you want a thicker sauce.
Turn off the heat and let the curry rest for a few minutes. Garnish generously with chopped cilantro or parsley, then serve hot with rice or crusty bread.
