Step 1: Prepare Mac and Cheese : In a large mixing bowl, combine cooked macaroni, cheddar cheese, Parmesan cheese, milk, Dijon mustard, salt, and pepper. Mix until well combined and creamy.
Step 2: Chill Mixture : Shape the mac and cheese into 12 balls and place them on a parchment-lined tray. Chill in the refrigerator for at least 1 hour to firm up.
Step 3: Prepare Breading Station : Set up three bowls: one with flour, one with beaten eggs, and one with breadcrumbs.
Step 4: Coat Mac and Cheese Balls : Roll each chilled mac and cheese ball in flour, dip into egg, and coat evenly with breadcrumbs.
Step 5: Fry : Heat vegetable oil in a deep skillet or pot to 350°F (175°C). Fry the balls in batches for 2-3 minutes or until golden brown and crispy. Remove and drain on paper towels.
Step 6: Prepare Dipping Sauce (Optional) : Mix mayonnaise, ketchup, hot sauce, and lemon juice in a small bowl. Serve alongside fried mac and cheese balls.
Step 7: Serve : Serve warm as an appetizer or snack with dipping sauce.