In a large pot, brown the sausage over medium-high heat.

Add the onions and garlic to the pot and sauté until tender, 2-5 minutes.

Add the sliced mushrooms and sauté until tender, about 5 minutes.

Transfer the sausage and vegetables into the pot of a slow cooker. Add in the tomatoes, basil, red wine, capers, salt, pepper and red pepper flakes. Cook on low for 6-8 hours. (You can serve it sooner, but the sauce will develop more flavor the longer you cook it.)

Just before dinner, cook the box of spaghetti noodles in salted water until al dente.

Open the slow cooker and stir in ¾ cup Parmesan cheese to thicken the sauce.

Drain the noodles and pour them into the sauce. Stir to combine thoroughly.

Spoon into a serving bowl and top with the remaining Parmesan cheese.