Dry roast all the ingredients in a frying pan on low heat for a couple of minutes. You know it's done when a strong, lovely aroma hits your nose, not a burnt one.
Transfer to a plate and let cool immediately.
Place in a food processor and blitz to a fine powder.
Store in a clean jar, in a cool place like all your other spices.
Video
Notes
Your garam masala will keep for months but like any other spice, its potency starts lessening with age.
To make more, just double or triple the quantities.
Have fun experimenting and making your own mix.