In a saucepan over medium-heat, add butter and when sizzling, add onion and celery; sauté for 1 minute. Add mushrooms and sauté for 2 minutes. Add flour and cook for 1 minute, stirring constantly. Pour in milk, add poultry seasoning, hot paprika, salt, and freshly ground black pepper; stir well and cook until the sauce thickens about 1 minute. Turn off the heat and add turkey and parsley; stir well. Transfer to a bowl and let cool off for 5 minutes before covering and chilling for 5 hours.
In a pot over medium heat, add oil and bring to 365ºF. Meanwhile, divide turkey mixture into 8 balls; set aside.
In a shallow plate, add breadcrumbs and season with black pepper; stir to mix. In another shallow plate, combine egg with milk; beat well. Roll each croquette into breadcrumbs then egg mixture and again in breadcrumbs.
Working in batches, carefully place them in hot oil and fry for 3 minutes or until golden brown. Transfer them to a plate lined with paper towels to absorb any excess oil. Serve with gravy or cranberry sauce along with mashed potatoes and veggies. Makes 8 croquettes.