Brown off the beef properly in a large pot. Don't rush this, colour is flavour.
Add the onion and mushrooms. Turn the heat down and let the residual heat do the work. You want them soft and sweet, not fried to death.
Stir in the tomato purée and garlic. Keep the heat low, don't burn the garlic. Let it cook out for about 5 minutes.
Add a good spoon of Dijon mustard, a splash of stock, and a decent handful of Parmesan. Stir and let it gently simmer.
Add your cooked pasta and the spinach. Fold everything together until the spinach wilts and the sauce clings to the pasta.
Finish with parsley and more Parmesan.
