Heat a skillet over medium heat and cook diced onion for 2-3 minutes until translucent. Add minced garlic and cook for 30 seconds. Add fresh spinach and sauté for 3-4 minutes until wilted. Press the cooked spinach with paper towels to remove all moisture, then let cool for 5 minutes.
1 small onion, 2 cloves garlic, 2 cups spinach
In a mixing bowl, combine the pressed spinach, crumbled feta, shredded mozzarella, beaten egg, salt, and black pepper. Stir until the egg evenly coats all ingredients and the mixture holds together when pressed.
2 cups spinach, 0.5 cup feta cheese, 0.5 cup mozzarella cheese, 1 large egg, to taste salt, to taste black pepper
Lay one phyllo sheet flat and brush lightly with olive oil (about 1 teaspoon) using a pastry brush. Place a second phyllo sheet on top and brush again. Cut the layered sheets lengthwise into 3-inch wide strips. Place 1 tablespoon of filling at the bottom of each strip, fold the corner over to form a triangle, and continue folding flag-style to the end of the strip. Press edges together to seal.
8 sheets phyllo dough, as needed olive oil
Preheat the air fryer to 350°F for 3 minutes. Place folded triangles seam-side down in the basket without touching each other. Brush tops lightly with olive oil. Cook for 10-12 minutes, rotating the basket halfway through for even browning, until phyllo is golden brown and crispy.
8 sheets phyllo dough, as needed olive oil
Remove the borek from the air fryer basket and place on a wire rack or plate. Let rest for 2 minutes before serving to allow the filling to set and prevent cheese from leaking immediately when bitten.
