Boil diced potatoes in salted water until fork-tender. Drain and mash with butter until smooth.
Stir in cornstarch and let the mixture cool completely.
Set up three bowls: flour; eggs beaten with a pinch of salt and pepper; and panko mixed with garlic powder, smoked paprika, and oil.
Flatten about 1 tbsp of mashed potato in your palm, place a cheese cube in the center, and wrap the potato around it into a small log shape.
Dip each croquette in flour, then egg, then panko, pressing to coat evenly.
Air fry at 400°F for 10-12 minutes, until golden and crisp.