Take a non stick pan and put on low heat. Remember, all the process needs to be done on low heat only.
Add cumin and coriander seeds. Dry roast till they slightly change their colour.
Take them out in a bowl.
Now put cloves, nutmeg, black pepper, red chillies and dry ginger in the pan. Dry roast till nice aroma comes out of them and they get roasted good.
Take them too out in the same bowl.
Now roast mint leaves till they slightly turn brown. Transfer them to the bowl.
Roast carom seeds for couple of seconds only because it gets burn immediately. This too needs to be transferred to the same bowl carrying all the ingredients.
Once all the roasted spices turn completely cool, transfer them to a grinder jar.
Add dry mango powder, salt, black salt, asafoetida and citic acid.
Grind them to a very fine powder.
Chaat masala is ready.
Notes
Instead of dry mint leaves, you can use fresh one also. Roast them till the point they turn dry and crisp.