Preheat your oven to 375°F (190°C). Line a small baking dish with foil or lightly oil it.

In a bowl, combine the chopped spinach, softened cream cheese, shredded mozzarella, grated Parmesan, minced garlic, Italian seasoning, and a pinch of salt and pepper. Stir until well mixed.

Pat the chicken breasts dry. With a sharp knife, slice a horizontal pocket into the thick side of each breast, leaving about 1/2 inch intact so it opens like a book.

Spoon the cheese-and-spinach mixture into each pocket. Don’t overfill — the filling should sit comfortably without bursting the seam.

Heat a skillet over medium heat and add a thin film of olive oil. When the oil shimmers, sear the stuffed breasts 3 to 4 minutes per side until they form a golden crust.

Transfer the seared breasts to the prepared baking dish. Bake for 20 to 25 minutes, or until an instant-read thermometer inserted into the thickest part reads 165°F (74°C).

Remove from oven and let rest for 5 minutes before slicing. Resting allows juices to redistribute.