Garam masala is a robust blend of many spices that often is used in Indian and Asian cuisines. One of the most important tips for making a good garam masala is that the resulting deep flavor comes from a layering not only of different spices, but often from the same spices prepared in different ways. Another aspect to making masala is to use as many whole spices as can be found and to avoid pre-ground spices when possible. The actual recipe for masala is different according to the taste of each person, so it is not necessary to use all the ingredients listed in a recipe if their taste is not appreciated. Many recipes for garam masala call for a wide variety of spices, so it can be beneficial to make a large batch all at once and store the extra spice in an airtight glass container.
The ingredients in garam masala can vary from one recipe to the next, but the most identifiable flavors come from cumin, coriander, cardamom, cloves, cinnamon and black peppercorns. To get the deep, rich flavor for which it is known, the spices should be roasted slowly in a dry pan until they are aromatic and then allowed to cool before being ground into a fine powder. In addition to the roasted spices, adding a small quantity of the cumin and coriander that is not roasted can bring some complexity to the mixture. It is difficult to roast pre-ground spices effectively, and the flavors will be slightly different because some of the oils that are in the whole spices will have dissipated if ground first.
Fennel and mace can be added to the mixture but will alter the flavor. The type of cardamom that is used usually is green, although black cardamom is included in some recipes. When using cardamom, it can either be shelled ahead of roasting or roasted in the pods and shelled after they have cooled. Although garam masala literally means "hot spice mixture", hot ingredients such as ground chili peppers generally are not added in significant quantities.
It does not take long to make garam masala, but so many Indian recipes call for its addition that it can be helpful to have some on hand. Roasting a larger quantity of spices at one time also can be more convenient than continually making the mixture as needed. When masala is made in advance and needs to be stored, it should be kept in a glass or other non-porous container with an airtight lid. Masala also should be stored in a cool place. Over time, the powder will tend to absorb moisture from the air and eventually will begin to release its oils, coating the container in which it is stored with a pungent film that is hard to fully remove from materials such as plastic or wood.