It’s important to let your potato mixture cool before breading and frying. If you’re unsure, feel free to refrigerate your tray of assembled cheese-stuffed potato balls overnight before breading and frying. Also, make sure you’re not getting too greedy with your cheese-to-potato ratio. Make sure there’s plenty of the potato mix protecting the cheese, which essentially turns into lava during frying. Delicious lava, but not particularly structurally sound lava.