Preheat Ninja Foodie at 390 degrees Fahrenheit for five minutes.
Toss the hearts, spinach, ginger and thyme in a large bowl until the hearts are completely coated.
Pour vegetable oil into preheated air fryer.
Evenly spread the hearts out on the cook and crisp plate.
Cook for 10 to 15 minutes, rotating every five minutes.
Allow to cool before serving.