Almost there

We are almost there. As you have been adding water (about 6-8 cups total- so reducing 3 times) I hope you added salt. Now put on another pot to boil your pasta. MAKE THE WATER SALTY LIKE THE OCEAN. No flavor in the water means no flavor in the pasta cook your pasta 1 minute less then directed. Save a cup of the pasta water you will need it later.
In a third large sautee pan (yes I know alot of pans) dump your cooked pasta and about 1/2 the sauce, stirring to combine.
Now remember that cup of pasta water ? Add it now. This is will aide in the pasta taking in the sauce you just spent 4 1/2 hours to make. Add mushrooms and let simmer for 2-3 mins. and serve with Parmesan chesse on top.