Preheat the oven to 400°F (200°C).
Slightly pound the thickest part of the chicken breast. Cut a slit in the chicken creating a pocket (cut the chicken breast horizontally, but not all the way through, see photos in the body of the post for a reference). If the chicken breasts have tenderloins attached, remove them and use them in another dish.
3 medium/large chicken breasts
Season the chicken breast with salt, pepper, paprika, onion powder, and garlic powder. You can proceed with the recipe right away, or let the chicken marinate for an hour (or longer) for a juicier result.
1 teaspoon paprika, 1 teaspoon garlic powder, 1 teaspoon onion powder
Heat butter in a pan (preferably a pan that you can put in the oven, but not necessarily) over medium heat and add garlic. Cook for 30 seconds, until garlic is fragrant.
1 tablespoon butter, 3 cloves garlic
Add spinach and cook until wilted and all the excess liquid is evaporated.
4 ounces (115g) fresh spinach
Transfer to a cutting board and squeeze out as much liquid as possible using paper towels. Chop the spinach and add to a medium bowl. Add cream cheese, 1/4 cup of shredded mozzarella, and parmesan cheese. Stir until combined and season with salt and pepper.
2 ounces (60g) cream cheese, 2 tablespoons grated parmesan
Divide the spinach mixture between each chicken breast, filling each pocket with the mixture. Close the pocket with toothpicks (it doesn't have to be completely closed).
Wipe the pan with paper towels and add the oil. Heat over medium heat. When hot add the chicken and sear on one side until browned, flip over and cook for 2-3 minutes.
Top with the remaining mozzarella cheese (1 cup) and cover the pan with a piece of aluminum foil.
Bake for about 20 minutes, or until the chicken is cooked through. It’s best to check with a thermometer. I use a grill thermometer, baking the chicken with the probe inserted while the thermometer stays outside the oven, with the wire running through the oven door. This allows me to monitor the internal temperature in real time. I remove the chicken when it reaches 160°F (71°C), as it will rise to the safe temperature of 165°F (74°C) while resting.
Let the chicken rest for 5-10 minutes before slicing and serving.
Enjoy!