Combine your beef mince, pork mince, breadcrumbs, onion, parsley, garlic, egg, parmesan, salt and pepper in a bowl with your hands until all your ingredients are evenly distributed.
Roll your mixture into small balls, then pan fry on a high heat until browned. Remove from pan and set aside.
Heat your oil in a medium sized saute pan and add your garlic and chilli flakes. Cook out for 2 mins until your oil starts to take on colour and is fragrant. Tip in your tomatoes and break up with the back of your fork. Simmer on a low heat for 45 mins or so until your sauce is reduced and delicious.Whizz until smooth with a stick blender, then add your seasoning and meatballs. Simmer for 5 mins until your meatballs are cooked through, then set aside.
In a small saute pan, melt your butter over a medium heat. Add your flour and cook out for a couple of mins until it starts to smell biscuity.
Gradually pour in your milk, whisking all the while so that your mixture becomes a smooth sauce. Add your cheddar, parmesan, nutmeg and seasoning and stir to combine. Keep warm.
Pour your cooked spaghetti into a large bowl and add your remaining ingredients. Stir until thoroughly combined.
In a rectangular dish greased with butter, arrange some of your spaghetti in the bottom. Top with a spoon of meatball mixture, béchamel and cheese. Repeat until you have done this on all layers.