Preheat oven to 375°. Separate each pita bread into two rounds. Brush cut sides with olive oil; then cut into small wedges. Place wedges on baking sheet. Set aside.
Heat a heavy, dry skillet on high setting; add pistachios and toast about 5 minutes, stirring often. Remove nuts to a medium-size mixing bowl.
In the same skillet, toast sesame seeds about 5 minutes, stirring often. Add seeds to pistachios in bowl. Repeat toasting process with coriander, cumin, and fennel, adding to same bowl. Add peppercorns, dried mint, and salt.
Use a mortar and pestle to crush ingredients until they’re the size of small breadcrumbs (or pulse in a food processor to a dry, coarse consistency, but be careful not to overprocess).
Sprinkle dukkah spice mixture evenly over oiled pita wedges and toast pita in the oven until golden brown, about 10 minutes.