Preheat the oven to 200°C.
Heat milk and bay leaves in a pan to scalding point, then remove to infuse.
Melt butter in a saucepan and stir in flour for three minutes without browning.
Remove bay leaves and gradually whisk milk into the flour mixture to form a smooth paste.
Add remaining milk, bring to a boil, then simmer for three minutes while stirring.
Stir in grated cheese and mustard, seasoning with salt and pepper to taste.
Sauté onion, garlic, and oregano in oil until soft, then let cool.
Mix the cooled onion mixture with minced beef and season well.
Form the meat mixture into small 2.5cm meatballs.
Fry meatballs in oil until browned all over and fully cooked through.
Fry sliced shallots in oil for two minutes, then stir in the cooked macaroni.
Combine pasta with tomatoes, oregano, meatballs, and cheese sauce.
Transfer to a dish, top with parmesan, and bake for 15 minutes.
Brown the top under a hot grill before serving.