Combine all the ingredients except the ketchup in a small saucepan, bring to a simmer and cook for 5-6 minutes until thickened.
Add ketchup and adjust seasoning to liking.
Cholay for Samosa Chaat:
Combine all the chole/cholay ingredients except chaat masala in a small saucepan, bring to a boil, simmer till the chickpeas are tender, approximately 10 minutes.
Mash a little to create a thicker 'gravy', you want some liquid left in there because it really adds to the overall dish.
Add chaat masala, and adjust seasoning.
For Yogurt:
Whisk together yoghurt, sugar, and cold water.
Assembling:
For each samosa chaat plate break up one heated samosa, ladle over a big spoon of the cholay mixture, drizzle over ¼-1/3 cup of your sweet yoghurt, then put about 2-3 tbsp each of imli ki chutney and red chutney, top with papri and chaat masala and a little cilantro.