Bring large pot of water to boil. Salt it well and cook bucatini until al dente. Drain well and set aside.
While pasta is cooking, remove sausage from casings and start cooking in a large, deep skillet over medium heat with onions. As meat cooks, break it apart in small pieces.
Once onion is tender, add in garlic and mushrooms and cook 2 minutes. Sprinkle in salt and pepper to taste.
Measure out cream and add to blender along with drained roasted red peppers. Blend about 20 seconds or until most of the red peppers have been pureed into the cream. I left mine slightly chunky.
Pour this mixture over the cooked meat and onions and bring to a gentle simmer then reduce the heat down to low. Toss with pasta, basil leaves and cheese until well coated. Taste and adjust seasonings. Serve immediately.