Prepare the Chicken:

1. Pat the chicken breasts dry with paper towels. Using a sharp knife, cut a horizontal slit into each breast about two-thirds of the way through to create a pocket. Season both sides with salt and freshly ground black pepper. Dredge each breast in flour, shaking off any excess.

Sear the Chicken:

2. In a large oven-safe skillet, heat 1 tablespoon of olive oil and the butter over medium-high heat until shimmering. Add the chicken breasts and sear for 2–3 minutes on each side until golden brown. Transfer the chicken to a plate and set aside.

Prepare the Filling:

3. In the same skillet, add the remaining 1 tablespoon of olive oil. Sauté the roasted red pepper strips and baby spinach over medium-high heat until the spinach is wilted, about 3–5 minutes. Add the minced garlic and cook for an additional minute until fragrant. Season with salt and pepper to taste. Transfer the mixture to a small bowl.

Stuff the Chicken:

4. Return the seared chicken breasts to the skillet. Carefully stuff each pocket with a portion of the roasted red pepper and spinach mixture, followed by a slice of mozzarella cheese. Secure the openings with toothpicks if necessary to keep the filling intact during cooking.

Bake:

5. Preheat the oven to 375°F (190°C). Place the skillet with the stuffed chicken into the preheated oven and bake for 20–25 minutes, or until the internal temperature of the chicken reaches 165°F (74°C).

Serve:

6. Remove the skillet from the oven and let the chicken rest for a few minutes. Remove any toothpicks before serving. Enjoy the stuffed chicken hot, perhaps alongside a fresh mixed greens salad or your favorite side dish.