Step 1: Prepare the White Sauce

1. In a saucepan over medium heat, melt the butter.
2. Add minced garlic and sauté for about 1 minute until fragrant.
3. Whisk in the flour and cook for 1-2 minutes until slightly golden.
4. Slowly pour in the milk and heavy cream, whisking continuously to prevent lumps.
5. Add Parmesan cheese, salt, pepper, Italian seasoning, and nutmeg. Stir until the sauce thickens (about 5 minutes). Remove from heat and set aside.

Step 2: Cook the Mushroom & Chicken Mixture

1. Heat olive oil in a large skillet over medium heat.
2. Add sliced mushrooms, salt, and pepper. Sauté for 5-7 minutes until softened.
3. Stir in shredded chicken, garlic powder, and onion powder. Cook for another 2 minutes, then remove from heat.

Step 3: Prepare the Ricotta Mixture

1. In a bowl, mix ricotta cheese and egg until well combined.

Step 4: Assemble the Lasagna

1. Preheat the oven to 375°F (190°C).
2. Spread a thin layer of white sauce on the bottom of a greased 9×13-inch baking dish.
3. Add a layer of cooked lasagna noodles.
4. Spread a portion of the ricotta mixture over the noodles.
5. Add the mushroom and chicken mixture.
6. Pour white sauce over the chicken and sprinkle with mozzarella cheese.
7. Repeat layers until all ingredients are used, finishing with a layer of noodles, white sauce, and mozzarella cheese.
8. Sprinkle Parmesan cheese on top.

Step 5: Bake

1. Cover with foil and bake for 25 minutes.
2. Remove foil and bake for another 10-15 minutes, until the cheese is golden and bubbly.
3. Let it rest for 10 minutes before serving.