Bring a pot of water to a boil and season liberally with kosher salt. Add the pasta and cook until just al dente. Reserve 2 cups of pasta water, drain the pasta and set aside. You can lightly toss the pasta with olive oil to keep it from sticking together.

In a large skillet, melt 1 tablespoon of butter with the olive oil over medium heat. Add the shallot, crushed red pepper, and garlic and cook for 2-3 minutes, stirring often until softened. Add the Italian sausage and use a wooden spoon to break it up. Cook until browned.

Once the sausage is browned, add the tomato paste and cook for 3-4 minutes, stirring often, until deeply red in color. Add the pasta water and use it to pull up any browned bits on the bottom of the skillet. Simmer for 3-4 minutes, until thick and then stir in the mascarpone, remaining butter, and cream.

Add the pasta to the skillet and stir in the parmesan cheese. Cook for 2-3 minutes and then season to taste. Divide the pasta into bowls and top with more parmesan and torn fresh basil leaves.