Bring a large pot of salted water to a boil and cook potatoes for 8–10 minutes until fork tender. Let cool slightly.
Mash potatoes until smooth and lump-free.
Add butter, salt, garlic powder, black pepper, cream, egg, chives, and mozzarella cheese. Mix well to combine.
Chill the mixture for 1 hour (or 30 minutes in the freezer) until firm.
Scoop about 2 tablespoons of the mixture and shape into balls.
Coat each ball in flour, then dip in beaten eggs, and finally roll in panko breadcrumbs.
Heat oil to 350°F (175°C). Fry Potato Cheese Balls in batches for 2–3 minutes until golden brown.
Drain on paper towels, sprinkle with salt, and serve warm.