Dry roast spices separately until fragrant and lightly smoking. Let cool completely.
In oil, fry curry leaves for 2-3 minutes if using.
Combine all roasted spices. Add mustard seeds and nutmeg.
Grind mixture into a fine powder using spice grinder or blender.
Transfer to an airtight container. Store in cool, dry place up to 6 months.
Use 2-3 Tbsp per recipe to season curries, meats, soups and more.