Wash, peel, and dry the sweet potatoes, cutting them into 1/2-inch cubes.
In a large bowl, add the sweet potato cubes, oil, and seasonings. Toss with olive oil, and make sure all of your potatoes are coated.
Add your sweet potatoes to the air fryer basket. Set the temperature to 400 degrees f and the cooking time to 12-14 minutes. Shake the basket frequently as the sweet potatoes cook up, and remove when fork tender.
While the sweet potatoes are air frying, add the butter to a small skillet and fold the sage leaves. Saute for a few minutes until the butter turns brown; remember to mix while the butter is cooking. Remove from heat; when the butter turns brown, set aside.
Toss the sweet potatoes, brown butter, and sage in a large bowl. Serve with fresh sage leaves.