In a large skillet, heat 2 tablespoons olive oil over medium-high heat for 2 minutes until sizzling hot. Sauté onions and garlic until tender and nicely browned, about 2-3 minutes.

Add spinach and sauté for 1 minute until soft. Set aside on a plate to cool for 5 minutes.

In a large mixing bowl, add ground chicken, sautéed onion-spinach mixture, breadcrumbs, Greek yogurt, dill, lemon juice, oregano, paprika, cumin, salt, and pepper. Stir well with a spatula to combine everything together (or use your hands to press the ingredients together to evenly combine).

Shape the ground chicken mixture into a firm ball. This helps the mixture bind together to yield firm patties. Cover the bowl with plastic cling wrap and refrigerate for at least 30 minutes or overnight.

Take ½ cup chicken mixture at a time and shape into patties using your hands. You should get about 12 patties.

Heat the remaining 1 tablespoon olive oil in a cast-iron skillet over medium-high heat for 2 minutes until sizzling hot. Place patties on the skillet (about 6 pieces per batch) and cook for 3-5 minutes until nicely seared and starting to brown up the sides. Flip the patties over and cook for another 3-5 minutes, until the internal temperature for the patties reaches 165 F as read on a meat thermometer.

Serve warm with a side of rice pilaf and sautéed vegetables, or serve in hamburger buns.