Preheat your oven to 375°F (190°C).

Cook the lasagna noodles according to package instructions until al dente, about 8-10 minutes. Drain and rinse under cold water.

Shred the rotisserie chicken using two forks, discarding skin and bones.

In a large skillet, heat 2 tablespoons of olive oil over medium heat and sauté the onion until soft, about 5 minutes.

Add 2 tablespoons of butter to the skillet and melt. Whisk in the flour and cook until golden brown, about 2 minutes.

Gradually add 2 cups of chicken broth and 1 cup of half and half, stirring until smooth. Simmer for about 5 minutes.

Stir in 2 cloves of minced garlic and 4 cups of fresh spinach, cooking until the spinach wilts, about 2-3 minutes.

In a bowl, mix together ricotta cheese, beaten egg, shredded mozzarella, grated parmesan, and chopped parsley until smooth.

Assemble in a baking dish: spread a layer of sauce, add noodles, half ricotta mixture, half shredded chicken, and a third of the sauce. Repeat layers and end with sauce and remaining mozzarella.

Cover with foil and bake for 45 minutes. Remove foil and broil for 2-3 minutes until cheese is golden.

Let the lasagna rest for 10 minutes before serving.