Prepare macaroni according to package directions. Drain the macaroni in a colander and set aside.
Add butter and flour to a large casserole to form a roux then steadily add the milk, stirring well after each addition until you have a smooth sauce. Bring to the boil, stirring constantly then add the cheddar, Parmesan, and mozzarella. Stir to combine and then season with salt and freshly ground black pepper. Add the macaroni to the sauce and stir to coat all the pasta in the sauce then remove the casserole from the heat and pour the macaroni into a large baking tray, lined with greaseproof paper. Use a spatula to flatten the top and then refrigerate for at least 30 minutes.
Once cooled, use a 10cm cookie cutter to cut out 6-8 rounds. Sandwich 4 slices of provolone between 2 rounds of mac and cheese and repeat until all rounds are used up.
Place flour, mustard powder, cayenne, garlic powder and mixed herbs in a bowl and season well with salt and pepper. Place the eggs, and bread crumbs in two other separate bowls.
Dip each sandwich in flour, then egg, and finally breadcrumbs, coating evenly.
Preheat vegetable oil to 180°C.
Place the macaroni sandwiches gently in oil and fry 3-4 minutes, until golden brown then remove with a slotted spoon and drain on a paper towel-lined plate. Keep warm in a low oven whilst you fry the remaining sandwiches.