Heat the vegetable oil in a heavy pan (cast iron works great).
Brown the ground meat thoroughly until you get a nice crust. This adds flavor and texture.
Add the finely chopped onions and sauté together with the meat for 3-4 minutes until softened.
Stir in black pepper, allspice, and salt.
Cook the macaroni according to package instructions, but flavor the boiling water with the beef broth cubes or broth. If the broth is low in salt, add 1 tsp salt to the water.
When the macaroni is cooked, drain well and return to the pot.
Mix the meat mixture thoroughly into the macaroni.
Prepare the egg and milk mixture by whisking the eggs into the milk one at a time. Add salt and white pepper.
Transfer the macaroni and meat mixture into a greased baking dish. Pour the egg and milk mixture evenly over it.
Sprinkle breadcrumbs over the top. Dot with butter or, for extra richness, shave thin slices of butter over the breadcrumbs.
Bake in a preheated oven at 200°C (390°F) for about 1 hour, until the top is golden and the casserole is set.
Let the casserole rest for about 10 minutes before serving.