Start with whole spices
Spices that can be toasted to good effect include peppercorns, star anise, cinnamon, cumin, coriander, juniper berries, clove, mustard seeds, and fennel seeds.
Heat a small pan over a medium heat
They are done when they start to smell fragrant and toasty
Some seeds will tell you they are done by moving around a bit or jumping in the pan. But a rich, toasted scent is the most reliable indicator. If spices begin to smoke, you’ve gone too far.
Remove from heat to prevent over-toasting
Option 1: Leave them whole
If you’ve toasted more spices than you need right away, you can leave them whole and save them for use within a week or two.
Option 2: Crush them
To make cracked spices, put them in a freezer Ziploc bag and crush them with a rolling pin, pan, or the flat side of a mallet. Or you could use a mortar and pestle, if you have one.
By the way, cracked spices work especially well in rubs for roasted or grilled meats, but they’ll toast as the meat cooks—no need to pre-toast.
Option 3: Grind them
Let the spices cool before grinding them to keep the volatile aromas from disappearing into thin air. You can use a mortar and pestle, spice mill, or coffee grinder (reserved just for spices) to grind spices down to the granularity you want. To get really fine particles, sift the ground spices.
Some spices, like cinnamon sticks, are not so easy to grind at home. In such cases, you may be better off with a small amount of newly purchased ground spice.