Take a mixing bowl and add ginger, green chilli and salt to your taste. Also add chaat masala, Cumin powder, Coriander powder and whole cumin.
Add curd and whisk really well. Make sure the mixture is lump-free.
now, Take an aluminum foil and prepare a small cup. Place this cup on the curd mixture. Place a few fresh curry leaves inside the cup.
Now, Place the piece of charcoal directly on top of a gas burner. With the heat on full, burn the charcoal directly over the flames, turning the charcoal around using long tongs, so the flames reach all sides of the charcoal. The charcoal might spark a little but I have not found this to be a problem however, You must be careful.
Once the coal is ready use the tongs to transfer the hot coal into the center of the cup.
Take a teaspoon of clarified butter or ghee and drop this over the hot coal. The coal will immediately start emitting a dense white smoke. have the lid ready and quickly cover the saucepan or dish. (do this part outside the kitchen windowsill, turn your fire alarm off, the smoke can leave a smokey aroma in the kitchen for a day or two)
Leave it for 30 to 45 mins.
After that, Remove the charcoal and a foil cup. Trash the curry leaves.
Once the cup is removed, Cover again with lid and refrigerate the mixture.
For serving, Take a serving glass and fill the glass half with curd mixture.