Trim the ends of the green beans and cut them into bite-sized pieces. If using fresh, blanch them in boiling water for 2-3 minutes and then cool them immediately in an ice bath.

In a large bowl, combine the blanched green beans, cream of mushroom soup, milk, and any optional add-ins. Stir until the green beans are evenly coated.

Preheat your air fryer to 350°F. This ensures even cooking and a crispy top.

Transfer the green bean mixture to an air fryer-safe baking dish. Spread it evenly for consistent cooking.

Place the dish in the air fryer and cook for 15 minutes. Check halfway through and stir if necessary for even cooking.

After 15 minutes, evenly sprinkle crispy fried onions over the top of the casserole and cook for another 5 minutes until golden brown.

Let the casserole cool slightly before serving. Enjoy as a side dish with your favorite main course.

Store any leftovers in an airtight container in the refrigerator for up to 3 days. Reheat in the air fryer or microwave before serving.