Peel the sweet potatoes and cut into even ½”- thick wedges. Cut the wedges in half lengthwise if they are very long. Toss the wedges with the oil and arrange in an even single layer on a rimmed baking sheet.
In a small bowl stir together the butter, miso paste and the whites of the green onions together until completely combined and set aside.
Roast the sweet potatoes for 20 minutes then flip the potatoes.
Use a spoon to drop the miso butter over the sweet potatoes and continue roasting until crispy and golden brown, about an additional 15 to 20 minutes. If the potatoes aren’t browned enough, broil them on high for just 1 to 2 minutes.
Arrange the potatoes on a serving platter and sprinkle with sea salt then top with sesame seeds and drizzle with sour cream. Garnish with the remaining green onions, cilantro leaves and sour cream and serve immediately.