Preheat your oven to 375 degrees Fahrenheit (190 degrees Celsius).
Slice each chicken breast horizontally at the thickest part, but not all the way through. Open up the chicken breasts like a book.
Stuff each chicken breast with 2 basil leaves, mozzarella slices, chopped spinach, and sun-dried tomatoes.
Season the chicken breasts with Italian seasoning, garlic powder, salt, and pepper.
Carefully seal the chicken breasts closed using three toothpicks, ensuring the filling is secure.
Heat an oven-safe skillet on the stovetop over medium-high heat. Add a tablespoon of oil from the sun-dried tomato jar, and one tablespoon of butter.
Sear the stuffed chicken breasts in the skillet until they are browned on each side, approximately 2-3 minutes per side.
Once browned, remove the chicken breasts from the skillet and set them aside on a plate.
Wipe out most of the oil from the skillet, leaving about a tablespoon.
In a bowl, prepare the creamy garlic sauce. Add the heavy cream, chicken broth, garlic powder, Italian seasoning, chopped garlic, and pecorino romano cheese. Whisk the ingredients together until well combined.
Return the seared chicken breasts, and the creamy garlic sauce to the skillet, pouring the creamy garlic sauce over them.
Place the skillet in the preheated oven and bake for 20-30 minutes, or until the chicken is cooked through and the sauce is bubbling.
Once done, remove the skillet from the oven (careful, it will be hot!). Allow the chicken to rest for a few minutes before serving.
Serve the One Pot Creamy Italian Stuffed Chicken with a side of pasta, rice, or broccoli. Enjoy!