01 - Preheat the oven to 375°F (190°C).
02 - In a medium bowl, mix spinach, feta cheese, cream cheese, garlic, dill, nutmeg, and red pepper flakes until well combined.
03 - Pat the chicken breasts dry. Using a sharp knife, carefully cut a pocket into the thickest side of each chicken breast, being careful not to cut all the way through.
04 - Season the chicken breasts inside and out with salt and black pepper.
05 - Stuff each chicken breast with the spinach-feta mixture. Secure the openings with toothpicks if necessary.
06 - Heat 1 tablespoon olive oil in a large oven-safe skillet over medium-high heat. Sear the stuffed chicken breasts for 2–3 minutes per side until golden brown.
07 - Drizzle with 1 tablespoon olive oil, then transfer the skillet to the preheated oven. Bake for 20–25 minutes, or until the chicken is cooked through and reaches an internal temperature of 165°F (74°C).
08 - Remove toothpicks before serving. Let rest for 5 minutes, then serve warm.