Place the baby yukon gold potatoes in a large pot and cover with cold water by about 2 inches. Add a generous pinch of salt. Bring to a boil over high heat, then reduce to a simmer and cook for 15 to 18 minutes, until the potatoes are fork-tender all the way through.
Drain the potatoes well and let them cool for about 5 minutes until you can handle them. Place each potato on a cutting board and use the bottom of a heavy mug or a flat spatula to press down firmly, smashing each potato to about 1/2 inch thickness. You want them flattened but still holding together.
In a small bowl, mix together the garlic powder, smoked paprika, onion powder, salt, and black pepper.
Brush both sides of each smashed potato generously with olive oil. Sprinkle the seasoning mixture evenly over the tops.
Preheat the air fryer to 400 degrees F. Arrange the smashed potatoes in a single layer in the basket, working in batches if needed. Air fry for 15 to 18 minutes, flipping once halfway through, until the edges are deeply golden and the surfaces are very crispy.
Transfer the smashed potatoes to a serving platter. Immediately sprinkle with grated parmesan cheese and chopped chives. Serve hot with sour cream on the side.