Sear and Poach the Chicken: Heat 1 tablespoon olive oil in a large enameled Dutch oven or soup pot over medium-high heat. Season chicken breasts on both sides with 0.5 teaspoon salt and black pepper. Sear chicken for 2-3 minutes per side until lightly golden (it will finish cooking in the broth). Remove chicken and set aside on a clean plate.

Sauté Aromatics & Mushrooms: In the same pot, melt the butter with remaining 1 tablespoon olive oil over medium heat. Add the diced onion and sliced cremini mushrooms. Sauté for 5 to 6 minutes until mushrooms are browned and onions are tender and translucent. Add minced garlic, Italian seasoning, and red pepper flakes; stir constantly for 60 seconds until deeply fragrant.

Make the Roux & Simmer Broth: Sprinkle 3 tablespoons of all-purpose flour over the sautéed vegetables. Stir well and cook for 1 to 2 minutes to cook off raw flour taste. Slowly pour in the chicken bone broth while whisking continuously to dissolve any browned bits from the bottom of the pot. Return the seared chicken breasts to the pot. Bring the soup to a lively boil, then reduce heat to medium-low, cover, and gently simmer for 12 to 14 minutes until chicken reaches an internal temperature of 165°F.

Shred Chicken & Cook Lasagna Noodles: Transfer the cooked chicken to a cutting board and shred using two forks. While the chicken rests, drop the broken lasagna noodle pieces into the gently boiling soup. Cook uncovered for 10 to 12 minutes, stirring occasionally to prevent noodles from sticking together, until al dente.

Add Cream, Cheeses & Greens: Reduce heat to low. Stir in the heavy cream, 0.5 cup of whole-milk ricotta, and grated Parmigiano-Reggiano until smooth and velvety. Return the shredded chicken to the pot and fold in the fresh baby spinach. Simmer for 2 minutes until spinach is perfectly wilted and bright green. Season with additional salt and freshly cracked black pepper to taste.

Garnish and Serve: Ladle hot soup into wide warmed bowls. Top each serving with a dollop of remaining ricotta, a generous handful of shredded mozzarella (which melts instantly into gooey cheese ribbons), fresh basil chiffonade, and extra cracked black pepper. Serve immediately with warm toasted garlic bread.