Pre-heat Air Fryer at 380°F (193°C). Set at 20 minutes.
Place marble (baby) potatoes in a bowl and drizzle oil all over, then gently toss to coat.
Place 4 rosemary sprigs on a greased Air Fryer tray and add the prepared marble (baby) potatoes. Season marble (baby) potatoes with salt and black pepper.
Insert the Air Fryer tray into the middle cooking chamber and Air Fry marble (baby) potatoes for 12 minutes or until the potatoes are soft and tender inside.
If the Air Fryer uses a basket, add the marble (baby) potatoes onto the crisper plate, then insert the basket into the Air Fryer unit and follow accordingly.
Scatter 5 pieces of marble (baby) potatoes onto a parchment paper-lined baking sheet. Smash air fried potatoes with the bottom of a glass, add freshly grated cheddar cheese, bacon, and top with more cheese.
Return to the Air Fryer cooking chamber and Air Fry for 1 to 3 minutes or until cheese has completely melted. Add 1 to 2 minutes more for golden crisp cheese. Do the same for the remaining batches of marble (baby) potatoes.
To speed up the cooking time of all the batches, use the second Air Fryer tray with the loaded smashed potatoes and insert below the middle cooking chamber.
Immediately Transfer Air Fryer Loaded Smashed Marble (Baby) Potatoes with flat kitchen tongs to a serving plate, garnish with the remaining fresh rosemary, and serve with ranch dressing on the side.
Notes
Air Fryer Marble (baby) potatoes are deliciously fragrant with the addition of fresh rosemary sprigs. For a traditional loaded smashed potatoes, garnish with fresh green onions.
Use freshly grated mild cheddar cheese as it melts better and easier.