Add the thyme, coriander, cumin and fennel into the cold pan. Heat the pan over low medium heat. As the pan heats, the spices get fragrant. Remove from the stove and transfer on the plate immediately because they will continue cooking in the hot pan and you will end up with burnt and bitter spices.  Allow to cool completely.

Grind pistachios together with sumac, thyme, coriander, cumin, fennel in a food processor or use a mortar and pestle. 

Transfer to a spice jar, add red chili flakes (if using), salt, sesame seeds and olive oil. Mix well to combine. Store in a jar or in an airtight container.

*Alternatively you can use ground spices and substitute pistachios with peanuts or walnuts. Make sure to toast them for the flavor.