In a small saucepan or frying pan, heat 2 teaspoons oil over medium heat. Once hot, add 1 tablespoon chana dal and 1 tablespoon split urad dal, then cook until golden. Next, add ½ teaspoon cumin seeds, 120 g shallots*, and 3 cloves garlic. Saute for a minute or so, or until lightly softened. Then add 6 dried red chillies, 2 medium tomatoes, ½ teaspoon sugar, and salt to taste. Cook, stirring occasionally, until soft and slightly jammy.
Add the chutney to a high-speed mixer-grinder and blend with 2 tablespoons water until you achieve a smooth, thick paste.
Heat 2 teaspoons oil in a small tadka pan. Once hot, add ½ teaspoon mustard seeds until they pop. Immediately add 1 sprig curry leaves and optionally, extra dried red chillies.
Pour the tempering over the chutney and serve.
Notes
* Shallots can be substituted for pearl onions or mild yellow onions. ** Add more water (1 tbsp at a time) for a thinner chutney.