Mix the chopped frozen spinach, feta, cream cheese, garlic and half of the salt in a medium sized bowl.
Cut a pocket into each chicken breast.
Separate the spinach and cheese mixture into three parts, and roll into thick logs. Stuff each log into the pocket you made in the chicken breasts. Season with remaining salt and pepper.
Heat the olive oil in an ovenproof pan set over medium high heat, then add the stuffed chicken, "top" side down. Cook for 5 minutes, then flip the chicken over.
Place the pan into the oven, and bake for 10 minutes. If your chicken breasts are extraordinarily thick, cook for 2 to 5 minutes longer, or until juices run clear when you poke the chicken with a fork.
Thanks to the spinach, this is one of the more nutritious ways of preparing chicken breasts. It also presents very well if you are entertaining. I can eat chicken everyday as long as I get creative in the preparation. I found this recipe on Basil & Bubbly and will continue to add this into the dinner rotation.