Dry roast the cumin seeds, coriander seeds, fennel seeds, cinnamon stick, peppercorns and red chilies in a skillet on low heat. Roast separately until fragrant. Set aside to cool.
Add the roasted spices along with amchoor powder, black salt, asafoetida and mint leaves to a spice grinder. Grind to a fine powder.
Store the ground chaat masala powder in an air-tight container away from moisture, heat and sunlight.