Generously spray a rectangular baking dish that fits in your air fryer with cooking spray.
In a large bowl, whisk together the condensed soup, sour cream, melted butter, chicken broth, salt, pepper, and garlic powder until smooth.
2 cups sour cream, ½ cup unsalted butter, 1 10 oz can cream of mushroom soup, ½ cup low-sodium chicken broth, 1 teaspoon salt, ½ teaspoon black pepper, ¼ teaspoon garlic powder
Stir in the shredded chicken, cooked spaghetti, and peas, coating everything evenly.
1 pound cooked chicken, 1 pound thin spaghetti, ½ cup frozen peas
Transfer the mixture into the prepared dish and spread it out evenly. Sprinkle mozzarella, cheddar, and Parmesan cheeses over the top.
1 ½ cups shredded mozzarella cheese, ½ cup shredded cheddar cheese, 2 tablespoons grated Parmesan cheese
Cover the dish with foil and place it in the air fryer. Cook at 350ºF (180ºC) for 15–20 minutes, until heated through.
Remove the foil and air fry for another 5 minutes, or until the cheese is golden and bubbly.
Allow the tetrazzini to rest for a few minutes, then garnish with fresh parsley and serve warm.
Fresh parsley