In a large, deep skillet, heat the olive oil over medium heat. Add the sausage and cook and crumble it until it starts to brown, about 5 minutes.
Add the onion and cook, stirring often, until softened and translucent and the sausage is well-browned, 5 to 7 minutes.
Add the oregano, fennel, red pepper, garlic and salt/pepper (to taste). Stir to combine.
Add the tomato puree, tomato paste and broth. Stir to make sure everything is well combined.
Dump in the (dried) pasta, and stir until it's totally coated in sauce. Turn the heat to low, and put the lid on the pan. Simmer, stirring occasionally, until the pasta has absorbed the liquid and is tender- about 20 minutes.
Turn off the heat. Add the mascarpone and stir to combine. Add the mozzarella and stir until it's melted. Add the Parmesan shavings and basil (tearing larger leaves as you add them). Garnish with more Parmesan shavings and basil, and serve right out of the pan.