Cook potatoes in boiling salted water until just cooked. Drain.
Melt ghee in a saucepan and fry garlic, ginger and chilli. Add turmeric, curry leaves and green masala paste and fry for about 2 minutes, or until fragrant.
Add potato, tomato, sugar and salt. Simmer on low heat, stirring occasionally, for 10 minutes, or until tomato begins to soften. Add