While you can used pre-packaged dried thyme here, I prefer to dry my own fresh thyme in the oven just before making this blend. The thyme retains a nice green color, the flavor is bright and fresh, and there is none of the mustiness you sometimes get with herbs or spices that are past their prime. It's one of those little details that make enough of a difference to be worth it.
4 tablespoons fresh thyme leaves, stripped from stems (or equivalent dried)
2 teaspoons ground sumac*
scant 1/2 teaspoon fine sea salt, or to taste
1 tablespoon toasted sesame seeds
Place thyme leaves on a baking sheet in a 300F oven until dry, just ten minutes or so. Just long enough that they'll crumble between pinched fingers. Let cool.
Use a mortar and pestle to grind the thyme leave finely. If your thyme is at all stem-y or fibrous, sift to remove any larger particles. Transfer to a small bowl, and aside.
Crush the sumac finely with the mortar and pestle, add the salt and crush with the sumac. Add the thyme back, and grind together a bit. Stir in the sesame seeds, taste, and adjust to your liking, perhaps with a bit more salt, or sumac, or sesame seeds. Any za'atar you might not use in the coming days keeps best refrigerated (or in the freezer) if you make a double or triple batch.
*If you're having a hard time finding sumac, check the spice rack at your local market (I've seen it at Whole Foods), specialty foods stores and/or Middle Eastern markets.
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