To make the Chaat masala, toast the coriander and cumin seeds in a dry frying pan over a medium heat until they release their fragrance. Tip into a pestle and mortar (or spice grinder) and grind to a powder. Stir in the rest of the ingredients and store in an airtight container.

To make the Brunch chaat, boil the potatoes for 15 minutes, or until just soft, then drain. Return to the pan and crush lightly with a fork. Heat the olive oil in a heavy-based frying pan over a medium heat. Add the crushed potatoes, along with 2 teaspoons of the Chaat masala or garam masala, and fry until just starting to colour. Add the drained cooked peas or chickpeas and the tomatoes, and continue to cook for a few more minutes until the potatoes are golden brown. Stir in the rest of the ingredients, reserving a few of the coriander leaves to top.

To finish, split between two or more plates. Spoon over plenty of yogurt and tamarind. Season with a pinch or two of kala namak or sea salt and scatter over the remaining coriander leaves. Serve with wedges of lime on the side.