In a large pot, heat the olive oil over medium heat. Add the diced onion and sauté until translucent, about 5 minutes. Stir in the minced garlic and cook for an additional minute until fragrant.
Add the Italian sausage to the pot, breaking it apart with a spoon. Cook until browned and cooked through, about 5-7 minutes. Drain excess fat if necessary.
Pour in the chicken broth and heavy cream. Stir in the dried basil, dried oregano, red pepper flakes, salt, and pepper. Bring the mixture to a simmer.
Add the broken lasagna noodles to the pot and cook according to package instructions, usually about 8-10 minutes, until al dente.
Once the noodles are cooked, stir in the fresh spinach and cook until wilted, about 2 minutes.
Remove the pot from heat and stir in the ricotta cheese until well combined.
Serve the soup in bowls, topped with shredded mozzarella and grated Parmesan cheese. Garnish with fresh basil leaves.