Preheat oven to 350° F.
Take cold chicken breasts, and make 4-5 slits in the top of each breast. Be careful not to cut all the way through the chicken breast - just enough to put filling inside.
If you haven't already, cook the bacon fully. Break or chop into 1-inch pieces. Set aside. In a small amount of the bacon fat, cook the fresh spinach until wilted.
For the cream cheese mixture, be sure that your cream cheese is at room temperature. In a small bowl, combine cream cheese, mozzarella cheese, spinach, garlic powder, and a pinch of salt and pepper. Combine mixture with a rubber spatula and transfer to a zip-top sandwich bag.
Cut a very small tip off of one bottom side of the zip-top bag, creating a pastry bag. Start to pipe the filling into each slit in the chicken breasts. Add the pieces of bacon into the slits once they are filled.
Place chicken on a sheet pan lined with parchment paper or foil. Bake at 350° F for 30 minutes or until the chicken reaches 165° F.
Remove chicken from the oven and let rest for 5 minutes before eating.
Serve with your favorite sides and enjoy.