Bring a sauce pot to medium-high heat. Once hot, add the sausage in pieces to the pot. Don't stir right away. Let the sausage sit for 2-3 minutes to develop a crust. Then stir occasionally until the sausage is browned and no pink remains. Remove the sausage from the pot and set aside.
If there is enough oil left over from the sausage, lower the heat to medium and add the shallots. If not add a tablespoon or 2 of olive oil. Saute the shallots for 4-5 minutes or until softened. Then add the garlic and tomato paste. Saute the garlic for a minute while the tomato paste begins to caramelize. Then combine everything by stirring together.
Add the crushed tomatoes to the pot. Bring to a simmer and then add basil, salt, and the sausage. Simmer for 20 minutes. While the sauce is simmering, bring a pot of water to a boil and boil your pasta. SAVE 1 cup of the pasta water to add to the sauce.
After 20 minutes of simmering, add half a cup of pasta water to the sauce. Stir and then remove from the heat. Stir in the heavy cream and the parmesan until the pasta reaches a pinkish color. Then add your pasta to the pot and stir until the pasta is coated with the sauce.
Serve with extra parmesan cheese and basil!
Notes
When browning the sausage, don't move it right away when adding it to the pot. Let it develop a crust before you stir it. Stirring it right away will result in steaming the sausage instead of searing it.
It is good to take the sausage out about 15 minutes before you're about to cook it so that the temperature gets closer to room temperature.
Stir the sauce occasionally while cooking to make sure it doesn't burn on the bottom of the pan.