To make the patties, place the pistachios in the small bowl of a food processor. Beat for a few seconds, crumble and then put in a medium bowl. Add the fresh arugula to the processor, pulse for a few seconds to coarsely chop, then add to the bowl with the pistachios. Continue with the onion and garlic, to form a smooth paste, and add to the bowl. Add the lamb, 1 tablespoon oil, ½ teaspoon salt, and a pinch of pepper. Mix well to combine and with wet hands, shape the mixture into about 20 patties. Each patty should be about 5 cm wide, 2 cm thick and about 40 g weigh.