Bring a large pot of salted water to a boil. Add the pasta and cook for 4 minutes. Reserve 1 cup of the pasta water and set aside. Then drain the pasta and leave it in the colander.
In the same pot you used for the pasta, melt 2 tablespoons of butter. Add the mushrooms and saute for 2 minutes over medium heat. Transfer to a bowl and set aside.
Melt the remaining butter in the pot and add the garlic, cook for 30 seconds. Then whisk in the heavy cream, half-n-half, and tomato sauce.
Add the pasta to the sauce and bring to a boil over medium heat. Cook for 4-5 minutes until al dente, adding in the broccoli during the last 2-3 minutes of cooking. Stir the pasta occasionally as it cooks.
Remove the pot from the heat. Stir in the Parmesan cheese and sauteed mushrooms. Add splashes of the reserved pasta water to thin the sauce to your desired consistency. Season with salt and pepper to taste.