Heat ghee/oil in a heavy based saucepan over high heat. Add green chillies and fry for a minute until starting to blister.

Add onions and fry until softened

Lower heat to medium, add garlic, ginger and curry leaves. Cook for 1 minute until garlic starts to turn golden and smells amazing.

Add tomatoes and cumin, cook until tomatoes start to break down and thicken to a paste - about 2 minutes.

Add lentils, water, tumeric and salt. Stir, bring to simmer, cover and simmer gently for 1 hour. Stir two or three times during the hour.

Remove lid and simmer gently for 30 minutes to thicken, stirring every now and then. The dal is ready when it has a consistency like porridge - some lentils should be intact but some have broken down to thicken the sauce.

Stir through garam masala at the end. Adjust salt if desired