Cook spaghetti pasta until tender, about 10 minutes.
Meanwhile, heat oil in a frypan and saute onion and garlic, add the mince and brown.
Stir in the tomato puree and bring to the boil. Reduce the heat and simmer, covered, for 15 minutes.
Stir in the parsley and sugar and simmer uncovered for another 5 minutes.
Sauce: melt the butter and stir in flour, cook for 20 seconds, then slowly add the milk, stirring constantly. Keep stirring and let thicken, then simmer for 3 minutes or so. (Add cheese to this if you want to make it a cheese sauce rather than a white sauce. Both are nice.)
Now, place half of the cooked spaghetti over the bottom of a casserole dish (square or rectangular works well), top with the meat mixture, then the rest of the spaghetti. Pour white/cheese sauce over the top of this and then sprinkle with grated cheese.
Bake at 180 degrees C for 15 mins.
Let it sit after taking out of the oven for a while, makes it easier to serve and is not so hot for eating.
I have successfully doubled and trebled this dish to serve a crowd, I have also added grated carrots and zucchini to the mince mixture, in fact you could add all sorts to this and it would still be delicious. I have added a beef stock cube to the mince in the past too. Hope you all enjoy this.