– 3 tablespoons butter (salted), divided – 1 small red onion, minced – 1 supermarket rotisserie chicken, minced and shredded finely – ½ teaspoon pepper (freshly-cracked, or ground) – 1 teaspoon minced parsley – ⅓ cup all-purpose flour – 1 cup milk (whole or skim) – 1 teaspoon salt, (or to taste) – 2 egg (medium), beaten – 2 cup breadcrumbs, or panko (see notes) – 3 cup oil for frying
Heat 1 tablespoon of butter over medium-low heat. Cook the onion stirring it until it turns translucent (2-3 minutes). Stir in the chicken and stir until it is heated through. Season with pepper, and parsley. Set aside.
Heat the remaining butter over medium-low heat until it's melted. Add the flour all at once and whisk vigorously until it's combined with the butter. Cook stirring for two minutes. Add milk slowly while still whisking. Once all the milk has been added, keep stirring until the sauce starts to thicken. Season with salt to taste. Once it thickens enough that it starts lifting from the bottom of the pot remove from the heat. Stir in the chicken until it's combined with the bechamel base. Stir until it cools down a bit.
There are two ways to form them. You can put the mixture in a pastry bag. Extrude it onto a greased tray or a tray lined with a silpat. Or form them one by one shaping them to the size of wine corks. Cover with plastic film and refrigerate for at least 3 hours.
Remove from the fridge. If you used a pastry bag, cut them into similar-sized croquettes. Dip the croquettes in the eggs, then cover with breadcrumbs. Cover and freeeze for 3 hours, or refrigerate overnight.
Heat oil over high heat (375 ºF [190 ºC]) in a small saucepan (there should be enough depth to cover the croquettes). Remove the croquettes from the freezer and immediately Fry two by two until they turn golden brown. Rest on a paper towel to drain excess oil before serving.
They are best served freshly fried, but you can serve within an hour at room temperature.