In a mixing bowl, combine the mashed potatoes and grated cheddar cheese. Mix well.

Season the mixture with salt and pepper to taste.

Take small portions of the potato mixture and shape them into croquette shapes.

Place the plain flour, beaten egg, and breadcrumbs into three separate shallow bowls.

Dip each croquette first into the plain flour, then into the beaten egg, and finally coat with breadcrumbs, ensuring each croquette is evenly coated.

Heat vegetable oil in a frying pan over medium heat.

Fry the croquettes in batches until they are golden brown and crispy on the outside, about 2-3 minutes per side.

Once cooked, remove the croquettes from the oil and drain on kitchen paper to remove excess oil.

Serve hot and enjoy your cheesy potato croquettes!