Heat the olive oil in a large Dutch oven or stockpot over medium-high heat. Add the Italian sausage and cook, breaking it apart with a spoon, until browned and cooked through, about 5-7 minutes. Remove the sausage with a slotted spoon and set aside.

Add the diced onion to the pot and cook until softened, about 5 minutes. Add the minced garlic, dried oregano, and red pepper flakes, and cook for another minute until fragrant.

Pour in the crushed tomatoes and chicken broth. Bring the mixture to a simmer, then reduce the heat to low, cover, and let it cook for 15 minutes to allow the flavors to meld.

Reduce the heat to low and stir in the heavy cream and grated Parmesan cheese until the cheese is melted and the soup is creamy.

Return the cooked sausage to the pot. Add the fresh spinach and stir until it has wilted, about 2-3 minutes. Season with salt and pepper to taste.

Ladle the hot soup into bowls. Garnish with extra Parmesan cheese and serve immediately with crusty bread for dipping.