- Heat oil in a saucepan, add finely diced onion and cook over a medium heat for 5 minutes. Add chopped garlic and mince, stirring to break up the mince with a wooden spoon. Stir in the tomato sauce and bring to the boil, then turn down the heat and simmer gently for 15 minutes. Season with chopped fresh oregano and salt and pepper to taste.
- Cook spaghetti in boiling, salted water for 10 to 12 minutes or until just tender to the bite. Drain well.
- Heat oven to 190 degC. Spoon the meat mixture into the base of a lightly oiled lasagne dish or ovenproof baking dish. Arrange the spaghetti in a layer on top of the meat.
- Melt the butter in a saucepan. Stir in the flour and cook for 1 minute, stirring continuously. Remove from the heat and whisk in the milk until blended. Return to the heat and cook for 3 minutes, stirring until the sauce thickens.
- Stir in the grated cheese and season with salt and white pepper. Pour sauce over the spaghetti. Bake for 35 to 45 minutes or until golden brown.