Melt the butter in a large 12-inch deep cast-iron skillet or Dutch oven over medium heat. Add the diced yellow onion and cook for 3-4 minutes until softened and translucent.

Stir in the minced garlic, Italian seasoning, and freshly grated nutmeg. Sauté for 60 seconds until fragrant and aromatic.

Pour in the chicken bone broth, whole milk, heavy cream, sea salt, and black pepper. Stir well and bring the mixture to a gentle boil.

Submerge the broken lasagna noodles into the simmering liquid, separating them slightly with tongs to prevent sticking. Reduce heat to medium-low, cover with a lid, and simmer for 12-14 minutes, stirring every 3-4 minutes, until the noodles are al dente and the sauce has reduced into a velvety, creamy coating.

Uncover the skillet. Stir in the shredded chicken breast, fresh baby spinach, and grated Parmigiano-Reggiano. Cook for 2 minutes until the spinach is wilted and the chicken is warmed through.

Drop spoonfuls of creamy ricotta cheese evenly over the top of the pasta. Sprinkle generously with the shredded mozzarella cheese.

Cover the skillet for 3 minutes over low heat until the mozzarella is completely melted and gooey (or broil on high for 2-3 minutes until golden and bubbling).

Garnish with fresh chopped parsley or basil, let rest for 5 minutes to settle, and serve hot directly from the skillet!