In a medium skillet, toast the coriander and cumin seeds over moderate heat, shaking the pan, until golden and fragrant, about 3 minutes. Spread the spices out on a plate and let cool completely, then finely grind in a spice grinder. In the same skillet, toast the sesame seeds over moderate heat until golden, 2 to 3 minutes. Transfer the sesame seeds to the plate to cool. Add the coriander, cumin, sesame seeds and thyme to the food processor along with the pistachios, cayenne and 1 teaspoon each of salt and pepper and pulse until finely ground. Transfer the <em>dukka</em> to a bowl.