First Step: Prepare the FillingHeat olive oil in a skillet over medium heat. Add minced garlic and sauté for about one minute until fragrant but not browned. Add chopped spinach directly (fresh or frozen) to the skillet and season with a pinch of salt and pepper. Sauté until the spinach has wilted and excess moisture evaporates, approximately 3 to 5 minutes. Alternatively, microwave spinach for 45 seconds if you prefer quicker preparation. Remove from heat.

Second Step: Combine IngredientsTransfer wilted spinach to a mixing bowl. Add half of the shredded mozzarella cheese and the crumbled feta cheese. If using optional add-ins like sun-dried tomatoes, olives, ricotta, or Greek yogurt, fold them in now to create a creamy, flavorful filling.

Third Step: Prepare BreadButter one side of each bread slice generously. This buttered side will form the golden crust when grilled. Preheat a skillet or griddle pan over medium-low heat to ensure even cooking without burning.

Fourth Step: Assemble and CookPlace two slices of bread buttered side down on the skillet. Evenly distribute the spinach and cheese mixture over these slices. Add the remaining mozzarella cheese on top of the filling along with a pinch of crushed red pepper flakes if desired. Cover with the remaining bread slices, buttered side facing out. Cook for about 4 to 5 minutes on each side, pressing gently with a spatula to ensure even browning and melting. Adjust heat as necessary to prevent burning while allowing the cheese to melt fully inside.

Final Step: ServeRemove grilled cheese sandwiches from the skillet once both sides are golden brown and crispy. Let them rest for a minute, then cut in half diagonally. Serve hot with dips like tomato soup or ranch dressing, or enjoy on their own for a satisfying Mediterranean-inspired meal.