Preheat & Sauté Spinach: Preheat your oven to 375°F (190°C). Heat 1 tablespoon of olive oil in a large oven-safe skillet (cast iron works best) over medium heat. Add the fresh baby spinach and minced garlic. Sauté for 2 to 3 minutes just until wilted. Transfer to a cutting board, let cool for 2 minutes, and roughly chop.

Mix the Creamy Filling: In a medium mixing bowl, combine the chopped sautéed spinach, softened cream cheese, shredded mozzarella, grated parmesan, 1/4 teaspoon sea salt, and optional red pepper flakes. Mix with a fork until thoroughly combined and creamy.

Cut the Pockets & Season: Pat chicken breasts completely dry with paper towels. Place your palm flat on top of a chicken breast, and use a sharp chef's knife to carefully slice a horizontal pocket into the thick side, cutting about 3/4 of the way through without slicing through the back or opposite edge. In a small ramekin, mix smoked paprika, garlic powder, dried oregano, 1/2 teaspoon salt, and black pepper; rub all over the exterior of the chicken breasts.

Stuff & Secure: Spoon an equal amount of the creamy spinach mixture (about 2 to 3 tablespoons) into the pocket of each chicken breast. Press the edges closed and secure with 2 to 3 wooden toothpicks inserted horizontally to keep the filling enclosed.

Sear & Bake: Wipe out the skillet and heat the remaining 1 tablespoon of olive oil over medium-high heat. Place the stuffed chicken breasts into the hot skillet. Sear undisturbed for 3 to 4 minutes until deeply golden brown, then carefully flip and sear the other side for 2 minutes. Transfer the skillet directly into the preheated oven and bake for 14 to 15 minutes, or until the internal temperature reaches 165°F (74°C) in the thickest part of the meat.

Rest & Serve: Remove the skillet from the oven. Let the chicken rest for 5 minutes in the pan juices so the melted cheeses set slightly and the meat reabsorbs its natural moisture. Remove toothpicks, slice crosswise into thick medallions, and serve warm.