To make the curry powder, dry roast the coriander, fennel and cumin seeds in a small frypan over a low heat - individually - until aromatic. Combine all these with the curry leaves, and over a low heat, dry roast for about 5 minutes more. Do not burn. Grind the spices and leaves using a mortar and pestle or a clean coffee grinder. Set aside.
Place potato cubes in a microwave-safe bowl, and microwave until about 1/2 cooked (time depends on individual microwave), about 3 to 5 minutes. You could also steam or boil the potatoes.
In a large frypan, melt the ghee over medium heat. Cook the onion, garlic, and ginger in the ghee until golden and aromatic. Meanwhile, grind the remaining coriander and cumin seeds; add with one teaspoon of the curry powder (prepared in the first step) to the onions and garlic. Cook, stirring, for 30 seconds. Stir in the potatoes, and cook for 3 minutes. Stir in the coconut milk, bring to a simmer, and then reduce heat to low. Cover, and cook until potatoes are tender, about 7 minutes. Season with salt to taste. Top with chopped fresh coriander and serve.