In a large pot, heat the olive oil over medium heat. Add the diced onion and sauté for about 3-4 minutes until translucent. Stir in the minced garlic and cook for an additional minute until fragrant.
Add the Italian sausage to the pot, breaking it up with a spoon. Cook until browned and cooked through, about 5-7 minutes. Drain excess fat if necessary.
Pour in the chicken broth, and add the dried oregano, dried basil, and red pepper flakes if using. Bring the mixture to a simmer.
Stir in the heavy cream and bring back to a gentle simmer.
Add the broken lasagna noodles and cook for about 10-12 minutes, or until the noodles are tender. Stir occasionally to prevent sticking.
Once the noodles are cooked, add the fresh spinach, ricotta cheese, mozzarella cheese, and Parmesan cheese. Stir until the cheeses are melted and the spinach is wilted. Season with salt and pepper to taste.
Serve hot, garnished with fresh basil if desired.