Place all the sumac yogurt ingredients in a medium bowl and whisk with a fork until all the ingredients are combined. Option to sprinkle a bit of sumac and drizzle of olive oil on top for presentation
Now make your patties. Start by adding your ground beef to a big mixing bowl and grating a medium onion on the largest grate setting
Add your pistachios into the bowl of a food processor and blitz for a few seconds until roughly chopped, then add to the ground beef bowl
Place your arugula on a cutting board and roughly chop, then add to the bowl of ground beef and pistachios
Grate your garlic cloves into the beef bowl using a microplane or lemon zester
Add 2 TBSP extra virgin olive oil, 1.5 teaspoons of salt and about 1/2 teaspoons of freshly ground black pepper
Mix well to using your hands then with wet hands, shape the mix into about 30-40 patties (each patty is about 2 inches wide, 3/4 inch thick, and weigh about 1 1/2 ounce).
Put 1 tablespoon of olive oil into a large nonstick frying pan and place over medium heat. Once hot, add as many patties can fit without crowding the pan
Cook for about 3.5 minutes per side, until golden brown and just cooked through. Add another tablespoon oil to the pan between batches if needed. When the patties are all cooked, pile them onto a large platter and serve with the sumac yogurt sauce. If eating this as a meal, serve on a bed of rice or a bed of arugula and some shaved parmesan
