Sauté fresh spinach with minced garlic and Italian herbs in olive oil until wilted. Drain excess moisture by squeezing spinach in a fine mesh sieve or cheesecloth. Transfer to a bowl and mix in cream cheese and shredded mozzarella.
Pat dry chicken breasts, then carefully slice a horizontal pocket in each breast without cutting all the way through. Pound the chicken between plastic wrap to even thickness.
Stuff the spinach and cheese mixture evenly into each chicken pocket. Secure openings with toothpicks or kitchen twine to keep filling contained during cooking.
Season stuffed chicken breasts with salt, pepper, and preferred spices such as smoked paprika. Lightly brush with olive oil or melted butter.
Place stuffed chicken breasts in the air fryer basket in a single layer and air fry at 375°F (190°C) for 18-20 minutes, flipping halfway through, until internal temperature reaches 165°F (74°C).
Remove chicken from air fryer and let rest for 5-10 minutes before slicing to allow juices to redistribute and ensure juicy meat.