In a large oiled pan, sauté the onions and mushrooms over medium-high heat until slightly golden, about 5 minutes. Transfer to a plate.
Next, sauté the ground beef until just cooked. Drain if necessary.
Return the onions and mushrooms to the pan. Then add the tomatoes, sauce, sugar, salt and pepper, oregano, and basil. Bring to a boil then reduce the heat and simmer for 25 minutes, uncovered. (I cook the spaghetti while the meat mixture is simmering.)
Remove the pan from heat and add the meat mixture to the drained spaghetti. Stir to incorporate.
Place half of the mixture in a 9×13 baking pan, then sprinkle with half of the mozzarella cheese. Top with the remaining spaghetti mixture then sprinkle with the other half of the mozzarella and the Parmesan.
Bake at 375 degrees for 30 minutes. May be made in advance. Freezes well.
