From My Bowl

0 Cook the Pasta: Bring a large pot of water to a boil and add the salt. Add the pasta and cook until al dente, according to package instructions. Reserve 1 cup of pasta water for the sauce, then drain the pasta and set aside.
1 Cook the Sausage: In the meantime warm 1 tablespoon of the olive oil in a medium pan over medium-high heat. Add the sausage and use a spatula to break it into large crumbles. Sauté until the edges are crispy, stirring occasionally, 5 to 7 minutes. Remove from the pan and set aside.
2 Aromatics: Add the remaining tablespoon of oil to the pan and warm to medium heat. Add the onion and fennel to the pan and cook for 5 to 7 minutes, stirring occasionally, until the fennel is tender. Add the chili paste, tomato paste, and garlic; sauté for an additional 2 to 3 minutes.
3 Saucy: Deglaze the pan with 1/2 cup of the reserved pasta water. Bring to a simmer, stirring occasionally, and cook for 2 to 3 minutes,until the sauce is reduced by about half. Reduce the heat to low and add in the parmesan. Mix well, until the cheese has melted and a thick sauce forms. If the sauce is too thick, thin it out with ~2 tablespoon increments of reserved pasta water until it reaches your desired consistency.
4 Combine: Add the drained pasta and cooked sausage to the pan. Mix well until everything is evenly coated in sauce, then season with pepper and salt to taste if desired.
5 Serve & Store: Serve warm, topped with parsley and additional parmesan, or as desired. Store any leftovers in an airtight refrigerator in the fridge for up to 5 days.