Boil a large pot of salted water, add the penne pasta, and cook until al dente, about 10-12 minutes.
Heat olive oil in a large frying pan over medium heat. Remove the sausage meat from the casings and crumble it into the pan. Cook until browned, about 5-7 minutes.
Add the chopped onion and minced garlic to the pan with the sausages. Sauté until the onion is soft and translucent, about 3-4 minutes.
Pour in the chopped tomatoes, stir well, and let simmer for 10 minutes to thicken the sauce.
Stir in the double cream and bring back to a simmer. Add the spinach and cook until wilted, about 2 minutes.
Drain the cooked pasta and add it to the sauce. Toss to combine and heat through.
Serve the pasta topped with grated Parmesan cheese.