In a medium skillet, heat 1 tablespoon of olive oil over medium heat. Add minced garlic and sauté for about 30 seconds until fragrant.
Add the chopped spinach to the skillet and cook until wilted, about 2-3 minutes. Remove from heat and let it cool slightly.
In a mixing bowl, combine the cooked spinach, ricotta cheese, mozzarella cheese, Parmesan cheese, dried oregano, salt, and black pepper. Mix well until all ingredients are fully incorporated.
Using a sharp knife, carefully create a pocket in each chicken breast by slicing horizontally, being cautious not to cut all the way through.
Stuff each chicken breast generously with the spinach and cheese mixture, sealing the pocket with toothpicks or tying with kitchen twine.
Heat a couple of tablespoons of olive oil in an oven-safe skillet over medium-high heat. Once hot, add the stuffed chicken breasts and sear for 3-4 minutes on each side until golden brown.
Transfer the skillet to the preheated oven and bake for 25-30 minutes or until the chicken is cooked through (internal temperature should reach 165°F or 75°C).
Once cooked, remove the chicken from the oven and let it rest for 5 minutes before serving.
Remove toothpicks or twine, slice in half if desired, and serve warm.
Notes
Garnish with fresh herbs and serve with sautéed vegetables or a salad.