Adapted from Jo Cooks
Divide the mashed potatoes into even sized portions.
To each portion of mashed potato, place a cheese cube in the center and then form the potatoes into a ball around it. Repeat until all the potato and cheese are used.
Optional: Freeze the mashed potato balls for 20-30 minutes until solid.
Use a breading procedure to coat the potato balls: one bowl with flour, one with beaten eggs, and the third with breadcrumbs. Roll the croquettes in flour, then egg, then breadcrumbs until covered completely. Repeat until all croquettes are covered.
Heat oil then fry the croquettes in batches flipping or rolling them until they are golden brown on all sides. Set on cooling rack or paper towels.