Heat your largest skillet over medium-high heat. Add the oil.
To the sizzling pan, add the onion, mushrooms, and ground beef. Break up the meat and saute for 8-10 minutes until fully cooked and browned. If there is a lot of fat in the pan from the meat, drain until you have about 2 tablespoons of oil left in the pan.
Add the garlic, rosemary, salt, and pepper to the pan and cook for another minute.
Deglaze the pan with the stock or water. Bring to a simmer. Add the heavy cream and reduce the heat to medium low.
Meanwhile, cook and drain your pasta until al dente. Carefully save some starchy pasta water for later.
When the cream sauce has thickened, or after about 5 minutes, add the cooked and drained pasta to the sauce. Toss over low heat.
Add a few tablespoons of pasta water to the pan to emulsify the sauce, stirring frequently. Add in the Parmesan.
Garnish with chopped basil and serve.