Brown your Italian sausage over medium-high heat on the stove top. Drain any remaining grease. Set it aside.

Chop your tomatoes and spinach. See notes below. 

Wash your mushroom caps and remove the stems. 

Preheat your air fryer to 370 degrees.

Combine the sausage, spinach, tomatoes, and parmesan cheese. Using a spoon, stuff each mushroom cap till it is heaping full. 

You will have to cook two batches of mushrooms, so pair your larger ones in one batch and smaller ones in another to help them cook evenly. Place them in your air fryer basket and cook at 370 degrees: For the larger mushrooms, cook for 5 minutes. Then remove the mushrooms and top them with the shredded mozzarella. Continue cooking for another 3 minutes. For the smaller mushroom caps, cook at 370 for 4 minutes, remove from the air fryer and top with the shredded cheese and cook for another 3 minutes. Allow them to slightly cool and serve.