In a large saucepan of boiling salted water, cook the pasta according to instructions on the package, or until al dente. Drain.
In a saucepan over a hight heat, bring milk to the boil then remove from the heat and set aside. In a small saucepan melt butter then add the flour and stir constantly until golden brown. Gradually stir in the milk and whisk until thick and smooth. Add bay leaf, salt, pepper and nutmeg and simmer over low heat for 15 to 20 minutes, stirring frequently.
Preheat oven to 180 C / Gas 4.
In a frying pan, heat the olive oil and add the onions brown the mince breaking it apart with a spoon while cooking. Season with salt, pepper and allspice to taste.
Grease a casserole dish and add alternating layers of pasta and mince.
Remove bay leaf from the bechamel sauce and give it a good stir. Pour over the noodles, cover with aluminium foil.
Bake for 20 to 25 minutes. Uncover and bake for another 5 minutes until golden brown on top. Remove from the oven and serve hot.