Ingredients
4 tbsp coriander  seeds
2 tbsp cumin seeds
1 tsp ajwain (thymol) seeds
2-3 whole dry red chillies
3 tbsp black salt crystals
1/2 tsp citric acid
1 tbsp dry mango powder (amchoor)
1 tbsp salt
2 tsp garam masala
1 tsp white/black pepper (optional)

Method
Roast the first 3 ingredients seperately
and powder them with the chillies, black 
salt and citric acid.
Mix in the remaining ingredients.
Store in an airtight container.
Will keep well for years.