In a large pot, melt butter over medium heat. Sauté diced onion for 2–3 minutes until soft. Add minced garlic and cook for 1–2 minutes until fragrant.
Deglaze the pot with a splash of chicken broth, then add the remaining broth. Bring to a boil and add the chicken. Boil until cooked through, then remove the chicken, shred it, and set aside.
Lower the heat to medium and add cream cheese to the broth. Stir until fully melted and smooth.
Add broken lasagna noodles to the pot and boil until al dente, about 10–12 minutes. Stir occasionally to prevent sticking.
Return the shredded chicken to the pot. Stir in heavy cream, parmesan cheese, and fresh spinach. Cook for 2–3 minutes until the spinach is wilted. Season with salt, pepper, and red pepper flakes to taste.
Ladle into bowls and garnish with ricotta cheese, extra parmesan, and fresh basil. Serve hot with garlic bread or crusty bread.