Heat olive oil and butter in a large pot or Dutch oven over medium heat.
Add diced chicken, season lightly with salt and pepper, and cook for 4–5 minutes until lightly golden and cooked through. Remove chicken and set aside.
In the same pot, add onion and cook for 3–4 minutes until softened.
Stir in garlic, Italian seasoning, and red pepper flakes (if using). Cook for 30 seconds, just until fragrant.
Pour in chicken broth and bring to a gentle boil.
Add broken lasagna noodles and cook for 10–12 minutes, stirring occasionally, until noodles are tender.
Reduce heat to low. Stir in heavy cream, Parmesan cheese, ricotta cheese, and shredded mozzarella until smooth and creamy.
Return cooked chicken to the pot and stir to combine. Add spinach if using and cook until wilted.
Simmer gently for 2–3 minutes, then remove from heat. Taste and adjust seasoning.
Garnish with fresh herbs and serve warm.