Chestnuts give Rach's hot sausage ragu a unique flavor and texture.
If making homemade sausage, combine meat with wine and seasonings, and chill several hours or overnight before using for flavors to combine.
Heat olive oil in Dutch oven or deep skillet over medium-high heat. Add sausage and brown and crumble the meat. Add onion, garlic and rosemary, and cook to soften onions, 5-6 minutes. Add chestnuts and stir a minute more; add wine and deglaze the pan. Stir in stock then tomatoes, breaking them up with a spoon. Reduce heat and simmer 20-30 minutes at a low bubble.
Bring pasta water to a full boil. Salt water and cook pasta to al dente. Add a cup of starchy pasta water to the sauce just before draining pasta then combine pasta with sauce. Serve in shallow bowls topped with Parmigiano cheese.