01 -
Preheat oven to 200°C (390°F) or 180°C if using a fan-forced oven. Pat the chicken breasts dry. Cut a deep pocket into the side of each chicken breast, keeping the smooth side intact. Season the inside and outside with half the salt and black pepper.
02 -
In a heavy, oven-proof skillet, melt the butter over high heat. Add sliced mushrooms and cook for 3 minutes until starting to brown. Add garlic, thyme, and the remaining salt and pepper. Continue to cook for 2 minutes until mushrooms are golden. Stir in baby spinach and cook until wilted, about 30 seconds.
03 -
Carefully fill the pockets of the chicken breasts with the mushroom mixture. Top with sliced mozzarella cheese. Use toothpicks to close the openings as best as possible; a complete seal is not required.
04 -
Wipe out the skillet with paper towels. Add olive oil and heat over medium-high. Sear the stuffed chicken breasts for about 1½ minutes per side until golden.
05 -
Transfer the skillet with the seared chicken to the preheated oven. Bake for approximately 15 minutes, or until the internal temperature of the chicken reaches 65°C (149°F), checking the thickest part of the meat.
06 -
Remove the chicken from the oven and transfer to a plate. Loosely tent with foil and rest for 5 minutes before serving. Garnish or pair with side dishes as desired.