Preheat your oven to 375°F (190°C), ensuring it reaches temperature before placing the chicken inside.
In a skillet, warm the olive oil over medium heat. Once hot, add the minced garlic and sauté for about 1 minute, or until it becomes fragrant but not browned.
Introduce the chopped spinach to the skillet, stirring occasionally. Cook until the spinach is wilted, which should take around 2-3 minutes. Remove from heat and set aside to cool slightly.
In a mixing bowl, thoroughly combine the softened cream cheese, crumbled feta cheese, shredded mozzarella cheese, sautéed spinach, onion powder, black pepper, and salt. Mix well until the filling is smooth and all ingredients are evenly distributed.
Carefully create a pocket in each chicken breast: take a sharp knife and slice horizontally along one side of the breast, making sure not to cut completely through to maintain the structure.
Fill each chicken pocket generously with the spinach and cheese mixture. If necessary, secure the openings with toothpicks to prevent the filling from spilling out during cooking.
Arrange the stuffed chicken breasts in a baking dish. Squeeze fresh lemon juice over the tops of each breast for added flavor and moisture.
Bake the chicken in the preheated oven for 25-30 minutes, or until the chicken is cooked through and has reached an internal temperature of 165°F (75°C).
After baking, allow the chicken to rest for 5 minutes. Carefully remove any toothpicks before slicing to serve.
Notes
Serve alongside roasted vegetables or a fresh salad. Garnish with parsley for added color.