Finely chop the cooked chicken. I usually use leftover chicken, making sure there are no bones, and chop it very finely. In a skillet, melt the butter and sauté the finely chopped onion until soft. Add the flour and stir constantly so it doesn't burn.

Next, add the chicken and stir. Gradually pour in the milk while stirring constantly. Season with salt, pepper, and a little nutmeg. Continue cooking and stirring until the mixture thickens. Taste and adjust salt if needed. Transfer the mixture to a dish and let it cool.

In a bowl, beat the eggs. Place breadcrumbs on a plate. Using two spoons, shape the mixture into croquettes, dip them in the beaten egg, then coat with breadcrumbs. Heat oil in a skillet and fry the croquettes in batches until golden brown. Serve with salad or French fries.