Preheat your oven to 375°F (190°C).
Heat olive oil in a skillet over medium heat and sauté garlic for 1 minute.
Add the chopped mushrooms to the skillet and cook until browned, about 5-7 minutes.
Stir in chopped spinach and cook until wilted, about 2 minutes.
Remove the skillet from heat and add cream cheese, mozzarella, salt, pepper, and Italian seasoning.
Make a pocket in each chicken breast using a sharp knife.
Stuff each chicken breast with the mushroom mixture and secure with toothpicks.
Season the outside of the chicken breasts with salt and pepper.
Place the stuffed chicken breasts in a greased baking dish and bake for 25-30 minutes.
Remove the toothpicks and allow the chicken to rest for 5 minutes before slicing.
