In a large skillet over medium high heat, break up the Italian sausage and cook until browned and crumbly, about 7 to 9 minutes. Use a slotted spoon to transfer the browned sausage to a paper towel lined plate. Pour off as much of the grease as possible and return the pan to the heat. Add the garlic to the pan and stir until fragrant. Pour in the homemade chicken stock and bring to a boil, scraping the bottom of the pan to release all the lovely browned bits that were stuck. Add the heavy cream and return to a rapid boil until the cream is slightly thicker. Return the sausage to the pan, toss to coat, then add the spinach and grated cheese, then scoop the pasta from the water onto the top of the spinach. If you have already drained the pasta, add the reserved pasta water, too. Toss to evenly distribute, wilt the spinach, and melt the cheese. Toss in the thinly sliced basil and serve with extra grated cheese.
