Preheat your oven to 375°F (190°C).

Boil the lasagna noodles in a large pot of salted water according to package directions until al dente, about 8-10 minutes. Drain and set aside.

Melt the butter in a saucepan over medium heat. Whisk in the flour, black pepper, sea salt, garlic powder, and onion powder. Cook for 1-2 minutes until bubbly and golden brown.

Whisk in the whole milk gradually, stirring until smooth. Cook until gently boiling and thickened, about 6-8 minutes.

Stir in the cream cheese and ½ cup of jack cheese until melted and combined.

Fold the baby spinach into the white sauce mixture and set aside.

Mix ricotta cheese, beaten egg, parsley, and ½ cup jack cheese in a bowl until smooth.

Grease a baking dish lightly with cooking spray. Spread a thin layer of the white sauce to cover the bottom. Place three noodles side by side over the sauce.

Spread half of the ricotta mixture over the noodles. Distribute half of the cooked chicken on top and spoon one-third of the white sauce over the layers. Sprinkle with 1 cup each of mozzarella and jack cheese.

Layer with another three noodles, followed by the remaining ricotta mixture and cooked chicken. Top this layer with another cup each of mozzarella and jack cheese.

Add the final layer of noodles on top. Cover with the rest of the white sauce, and sprinkle with the remaining mozzarella and jack cheese.

Bake in the preheated oven for 30 to 35 minutes, or until bubbling and lightly browned.

Garnish with additional parsley before serving, if desired.