In a large bowl, combine the flaked cooked white fish and cold mashed potatoes, gently mashing them together with a fork until well combined but still slightly textured.

Add the finely chopped onion, red bell pepper, minced garlic, and fresh parsley to the bowl, tossing gently to distribute the aromatics evenly.

Stir in the beaten egg, dried breadcrumbs, and Creole seasoning, mixing thoroughly until a cohesive dough forms that holds its shape when pressed.

Divide the mixture and shape into 8 equal-sized round patties, approximately 2 inches in diameter and half an inch thick.

Heat the vegetable oil in a large skillet over medium-high heat until it shimmering hot, about 350 degrees Fahrenheit.

Carefully place the fish patties in the skillet and fry for 3 to 4 minutes per side, turning once, until they are beautifully golden brown and crispy.

Transfer the cooked fish cakes to a paper towel-lined plate to drain any excess oil, then serve hot with fresh lime wedges and spicy mayo.