Butterfly and season the chicken. Slice horizontally through the center of each chicken breast, stopping before cutting completely through. Open each breast to form a pocket that can hold the filling.

Season the exterior of the butterflied chicken breasts evenly with the salt, pepper, and smoked paprika. Set the prepared chicken aside.

Make the cheese and spinach filling. Place the softened cream cheese, Parmesan, feta, chopped spinach, and finely chopped sun-dried tomatoes in a small bowl. Mix thoroughly until the ingredients form a cohesive, creamy filling.

Fill the chicken breasts. Divide the prepared cheese and spinach mixture among the seasoned chicken breasts, placing the filling inside each pocket.

Secure the open edges of each breast with toothpicks to help contain the stuffing. A small amount of filling may escape during cooking, which is perfectly acceptable.

Cook the stuffed chicken. Set a skillet over medium heat and add the butter. Once the butter is hot and beginning to melt, arrange the stuffed chicken breasts in the skillet.

Brown the chicken on all sides, turning each breast carefully to encourage even cooking. Continue cooking until the thickest part of the chicken reaches an internal temperature of 165°F (75°C).

Rest and serve. Transfer the fully cooked chicken breasts from the skillet and allow them to rest for a couple of minutes.

Remove all toothpicks before serving. Serve the Christmas stuffed chicken breasts while hot.