Prep the oven and pan: Preheat your oven to 375°F (190°C). Set a large oven-safe skillet on the stove.
Make the filling: In a bowl, mix cream cheese, Greek yogurt, mozzarella, Parmesan, garlic, lemon juice, lemon zest, parsley, and 1/4 teaspoon salt until smooth.
Fold in the spinach. If using frozen spinach, squeeze out as much water as possible first.
Season the chicken: Pat the chicken breasts dry. In a small bowl, combine paprika, garlic powder, onion powder, remaining 3/4 teaspoon salt, and black pepper.
Rub evenly over both sides of the chicken.
Create the pocket: Lay each chicken breast flat. Using a sharp knife, cut a horizontal slit along the thickest side to form a deep pocket, leaving the opposite side intact. Don’t cut all the way through.
Stuff: Spoon the spinach mixture into each pocket, dividing evenly.
Don’t overfill—stop just before the seam won’t close. Secure the opening with 2–3 toothpicks each.
Sear: Heat olive oil over medium-high. When shimmering, add the chicken.
Sear 2–3 minutes per side until lightly golden. If your pan is small, work in batches to avoid steaming.
Bake: Transfer the skillet to the oven and bake 12–18 minutes, depending on thickness. The chicken is done when an instant-read thermometer reads 165°F (74°C) in the thickest part (not in the filling).
Rest and serve: Let the chicken rest 5 minutes.
Remove toothpicks. Spoon any pan juices over the top and serve warm.