Preheat your oil in a deep pan or pot to 180°C / 350°F, using a thermometer to monitor the temperature.
In a large mixing bowl, combine the shredded fried chicken with the beaten egg, finely chopped sautéed onion, thyme, and smoked paprika. Mix well until all ingredients are evenly incorporated.
Add the panko breadcrumbs to the mixture and fold in gently to help bind everything together. If the mixture feels too loose, sprinkle in a little more breadcrumbs until it holds shape.
Take about a tablespoon of the mixture and roll it between your palms to form an oval or round shape, roughly 2 inches long. Place each shaped croquette on a parchment-lined baking sheet to set briefly.
Lightly dust each croquette with flour, shaking off any excess. This helps them develop a crispy exterior during frying.
Carefully lower a few croquettes at a time into the hot oil, using a slotted spoon, ensuring not to overcrowd the pan. Fry for about 3-4 minutes, turning gently, until they are golden brown and crispy all over.
Remove the croquettes with a slotted spoon and drain on paper towels to remove excess oil. Repeat with the remaining shaped croquettes, maintaining the oil temperature.
Let the croquettes rest for a couple of minutes, then serve hot with lemon wedges or your favorite dipping sauce for a satisfying crunch and tender inside.