Preheat the oven to 425 degrees Fahrenheit.
Cut each of the four chicken breasts lengthwise to form a pocket. Be careful not to cut all the way.
Sprinkle the meat with salt, pepper, garlic powder and paprika and one tablespoon of olive oil. Stir the chicken around to coat in oil and spices, making sure to get inside the meat, too. Set aside while you prepare the stuffing.
If your thawed spinach seems wet, drain any water and dry it by squeezing it in a paper towel. In a medium bowl add the spinach, ricotta cheese, minced garlic and sprinkle with salt and pepper. Mix well.
Using a spoon or a butter knife divide the mixture into 4 equal parts (I usually flatten the mixture with a spoon and draw a cross on top to visualize 4 quarters).
Place a quarter of the spinach cheese mixture inside each chicken breast, close it and secure with toothpicks. Usually, 2 or 3 toothpicks will do the job.
Heat the remaining 1 tablespoon of olive oil in a skillet (I use a cast iron skillet) and saute the chicken for 4-5 minutes per side over medium heat.
Transfer the skillet to the center rack of preheated oven and finish cooking for about 15 minutes more, until the meat reaches 165 degrees Fahrenheit.
Take the skillet out of the oven, cover lightly with aluminum foil and let the chicken rest for at least 5 minutes before slicing. Don’t forget to remove the toothpicks before serving!