Place the yogurt in a bowl and add one cup of water. Stir until dissolved.
Place the chickpea flour into a medium bowl and add a bit of the yogurt and water mixture. Whisk to dissolve well. Pour in the rest of the water/yogurt, while continuing to whisk (this will help dissolve the chickpea flour).
In a pot, heat the oil to medium-low heat and add the mustard, fenugreek and cumin seeds. Let them cook for 1 minute.
Add the mango purée and the red chilies. Add the sugar, turmeric, cumin, coriander, chili powder and 1 cup of water. Season with salt and pepper, to taste. Mix.
Cook for 5 minutes.
Add the yogurt/chickpea flour mixture and cook for 3 more minutes or until desired thickness.
Carefully strain the soup into another pot to remove the seeds and chili peppers. Heat to desired temperature and adjust seasoning, if needed.
Serve in 4 small bowls. It can be served with Indian puri bread or on its own. You can add some more seeds as toppings, if desired.
Notes
*Optional: If you can’t find canned mango purée, you can make it by adding 3 cups of peeled mango chunks to a blender or food processor and process until creamy/smooth.