In a small bowl, mix together the yoghurt and sugar. Add enough water (5-6 tablespoons) to give the yogurt a slightly runny consistency.
Slice the baby potatoes into chunks (roughly the same size as your chickpeas) and boil in the microwave or on the stovetop until soft and tender.
To a large bowl, add the rinsed chickpeas, chopped potatoes, diced red onion, green chillies, green chutney, tamarind chutney, chaat masala, cumin powder, salt and HALF of the yoghurt mixture.
Mix everything until it is well combined. Stir in a few chopped coriander leaves (optional). Taste the chana chaat and adjust the salt as required. You can also add some lemon juice for extra tang.
Divide the chana chaat into two bowls or transfer to one large serving platter. Drizzle on the remaining yoghurt, and top with more green and tamarind chutneys. Sprinkle on a little more chaat masala, and top with pomegranate seeds, chopped onion and thin sev (optional).
Enjoy immediately!
Notes
Best served immediately.
If you wish to prepare the chaat ahead of time, stop after step 4 and store in an airtight container in the fridge for up to 1 day, then add the toppings just before serving.