Melt butter in a saucepan over medium heat. Add chopped onion and garlic, cooking until softened and fragrant. Stir in flour and cook for about a minute to create a smooth base.

Slowly whisk in the milk until the mixture becomes thick and creamy. Add salt, pepper, garlic powder, onion powder, paprika, and celery seed. Continue cooking until the sauce coats the back of a spoon.

Combine the creamy sauce with shredded chicken and fresh parsley in a large bowl. Mix well until the filling is evenly combined and coated. Cover and refrigerate for at least 1 hour until firm.

Once chilled, scoop portions of the chicken mixture and shape them into small oval croquettes or patties. Keep the shapes compact so they hold together during frying.

Prepare three bowls with flour, beaten eggs, and seasoned breadcrumbs. Coat each croquette in flour, dip it into the egg, and roll it in breadcrumbs until fully covered.

Heat oil in a deep skillet over medium heat. Fry the croquettes in batches until golden brown and crispy on all sides, turning occasionally for even cooking.

Remove the croquettes with a slotted spoon and place them on a paper towel-lined plate to drain excess oil. Serve warm with your favorite dipping sauce.