Heat a small skillet to medium-high and add all the spices. Using a wooden spoon, gently stir the spices until they become slightly golden brown and fragrant. You can also hold the handle of the skillet to gently toss the spices until they become toasted. This may take a couple of minutes, but the real indicator is when the cumin seeds are light golden and the cardamom pods slightly swell.
Remove the spices from the heat. Once they cool, place them in a medium or large heavy mortar and pestle and grind into a fine powder. Alternatively, grind the spices in a clean coffee grinder on the finest setting.
Store the garam masala in a stainless-steel container or an airtight jar and keep it in a cool, dark place. For optimal flavour, use within 9 to 12 months.
Notes
Take care not to toast the spices at a very high temperature, as they can quickly burn. If you find that medium-high heat is too high, reduce the heat to medium. A heavy bottomed skillet will also help prevent the spices from burning.