I have listed the water as optional if you are using a thick rich prepared pasta sauce then add it in, adjust the chili flakes to suit heat level, for ease --- for ease I have canned mushrooms listed you may of coarse use fresh sauteed if desired.
In a medium pot cook the ground beef with onion until no longer pink; drain all fat.
Add in garlic and chili flakes; cook stirring for 2 minutes.
Add in 4-1/2 cups prepared pasta sauce and 1 teaspoon salt; bring to a simmer over medium heat.
Reduce the heat to low and simmer uncovered for about 45 minutes stirring occasionally (if you find that the sauce is too thick add in water and continue cooking for another 20 minutes).
Season with more salt if desired and black pepper about halfway through cooking.
Meanwhile in a large pot cook the pasta in boiling water until about halfway cooked, leave fairly firm do not cook until soft as the pasta will cook more in the oven) drain and place into a large bowl.
Add in the meat sauce, two cans drained mushrooms and 2 cups mozzarella cheese; mix until well combined.
Spread into prepared baking dish.
Sprinkle the parmesan cheese over the top.
Cover with foil and bake for about 35-40 minutes.
Sprinkle with 1 cup (or more) mozzarella cheese and return to oven uncovered for another 3-4 minutes.