In a large pot or Dutch oven, heat olive oil over medium heat. Add diced onion and cook until softened, about 3–4 minutes. Stir in garlic, Italian seasoning, and red pepper flakes. Cook for another minute until fragrant.
Pour in chicken broth, diced tomatoes, and tomato sauce. Stir well and bring to a simmer.
Add the broken lasagna noodles directly into the simmering soup. Cook for 10–12 minutes or until the noodles are tender, stirring occasionally to prevent sticking.
Stir in shredded cooked chicken and heavy cream. Simmer for another 5 minutes to heat through. Season with salt and pepper to taste.
Add mozzarella and ricotta cheese. Stir until the cheese is melted and the soup becomes thick and creamy.
Ladle the soup into bowls and garnish with fresh chopped basil or parsley. Serve with crusty bread for dipping.