Heat the olive oil in a large saucepan over medium heat. Add the chopped onion and sauté until soft and translucent, about 5 minutes. Add the minced garlic and chopped rosemary, continuing to sauté for another 5 minutes until fragrant.

Stir in the tomato puree, mixing well with the onions and garlic. Pour in the chopped tomatoes, including their juices, and the vegetable stock. Bring the mixture to a boil.

Add the tortellini to the boiling broth and cook for 5 minutes, until the tortellini is tender.

Reduce the heat to low and stir in the single cream until well combined. Turn off the heat and add the spinach and half of the chopped basil leaves. Stir until the spinach is wilted. Season to taste.

Ladle the soup into bowls and garnish with the remaining basil leaves and parmesan shavings, if using. Serve with crusty bread.