Pre-ground chilli powder is convenient; however, the longer ground chilli peppers sit on the supermarket shelf or in your pantry, the more flavour they lose. The oils that give the chilli peppers their heat react with the oxygen in the air; over time, even the spiciest chilli powder will lose its bite. For the freshest chilli powder, grind your own. Making your own chilli powder also allows you to control its heat level and flavour profile: try a mix of smoky chipotle and sweet cascabel chillies, or temper the heat of cayenne peppers with some mild anchos.
Toast the dried chilli peppers in a dry frying pan over medium heat for about 5 minutes, or until they begin to turn brown. Toasting the peppers removes any residual moisture and brings out their flavour. You can also put the chilli peppers on a baking tray, then toast them in a 325-degree oven for about 8 minutes. Remove the chilli peppers from the pan and let them cool down. Remove the stems and seeds from the peppers, then tear them into small pieces.
Grind the chilli peppers by hand using a mortar and pestle. This method produces the best flavour, but is by far the most laborious and time-consuming. Place the torn-up chilli peppers into the mortar, or bowl, then grind them against the side and bottom of the bowl by turning the pestle in a circular motion. Continue grinding until the chilli peppers turn into a coarse powder.
Use an electric coffee or spice grinder to make the chilli peppers into powder. This method is the easiest and fastest, and produces the finest-grained chilli powder. Place the peppers into the grinder, then turn on the grinder. Use a dedicated coffee grinder for chillies and other spices to avoid flavouring your coffee beans with chilli.
Make chilli powder using a pepper mill or grinder. This method allows you to make freshly-ground chilli powder as needed. Tear or cut the chilli pepper into the smallest possible pieces, then fill the empty pepper grinder with the chillies. Whenever you need chilli powder, just grind out the amount you need as you would pepper.
Move the ground chilli peppers to an airtight container. Store the container in a cool, dark cupboard, or in the refrigerator.
For a hotter chilli powder, leave some of the seeds in. Clean the coffee grinder thoroughly after grinding chilli peppers in it.
The dust created by grinding chilli peppers in a coffee grinder can irritate your nose, mouth and eyes; wear a medical mask and goggles to prevent this.