Heat your oven to 200C. Combine the breadcrumbs and milk and allow to soften. Heat a small frying pan over medium heat, add the oil and fry the onion and garlic for about 3 minutes until softened and fragrant. Pour the mixture into the breadcrumbs. 

Combine the breadcrumbs with the beef and pork mince, egg, mustard, Vegemite (if using) and season well with salt and pepper. Grease a large loaf tin and line with overlapping slices of prosciutto laid at right angles to the length of the tin. Fill the tin with the meat mixture and fold any overlapping ends of prosciutto over the top. Bake for 1 hour until the meatloaf is cooked through, then remove from the oven and turn the oven onto a high grill setting.

While the meatloaf is cooking, make the tomato sauce. Heat a small frying pan over medium heat, add the oil and fry the onion and garlic for about 3 minutes until softened and fragrant. Add the tomato passata and season well with salt and pepper. Cover and simmer for 30 minutes, then stir through the tomato sauce and butter. 

Turn out the meatloaf onto a lipped, ovenproof serving dish and pour over the tomato sauce. Scatter liberally with the cheese and grill until the cheese is browned and bubbling. Sprinkle over the parsley to serve.