Prep. Preheat oven to 375˚F. Lightly grease a 9 x 13 baking dish with cooking spray. *see notes
Sauté. Heat olive oil in a skillet over medium-high heat. Add garlic and cook for 20 seconds. Stir in spinach and sun-dried tomatoes; cook for 2 minutes, or until wilted. Stir frequently.
Make the cheesy filling. Season the spinach and tomato mixture with Italian seasoning and stir in the cream cheese; cook for 1 minute, stirring until the cheese is melted and the mixture is smooth and creamy. Remove from heat and set aside for 2 minutes.
Prep the chicken breasts. Cut 5 to 6 slits/pockets on top of each chicken breast and season with salt and pepper. DO NOT cut through - cut about 3/4 of the way down and keep the base of the chicken breasts intact.
Stuff the pockets. Place the chicken breasts in the baking dish and fill each pocket of the chicken breasts with the cheesy spinach mixture.
Bake. Transfer the chicken breasts to the oven and bake for 20 to 25 minutes, or until the chicken is cooked through. Use a meat thermometer to check for doneness - chicken is cooked at 165˚F. Cooking time will depend on the thickness of the chicken breasts.
Rest, then serve. Remove the chicken from the oven and let it rest for 5 minutes before serving.
Notes
Skillet options: To minimize cleanup, use an oven-safe skillet for the spinach mixture, and use the same skillet to bake the chicken breasts.
Storage: Refrigerate leftovers in an airtight container for 2-3 days.