1. 1. Prepare the béchamel sauce by melting butter in a saucepan over medium heat. Whisk in an equal amount of all-purpose flour to create a roux, cooking for 2-3 minutes.

2. 2. Gradually pour in warm milk, whisking constantly to prevent lumps from forming. Bring to a simmer and cook until thickened, about 10-15 minutes.

3. 3. Season the béchamel with nutmeg, salt, and pepper to taste.

4. 4. Cook lasagna noodles in salted boiling water according to package instructions, typically 8-12 minutes. Drain and rinse with cool water.

5. 5. Preheat the oven to 375°F and grease a 9×13 inch baking dish.

6. 6. Spread a thin layer of béchamel sauce in the baking dish. Layer cooked lasagna noodles, more béchamel sauce, shredded chicken, sautéed vegetables, mozzarella cheese, and Parmesan cheese. Season with garlic powder, salt, and pepper.

7. 7. Repeat layering two more times, ending with béchamel sauce and cheeses on top.

8. 8. Cover with foil and bake for 25 minutes. Remove foil and bake for an additional 10-15 minutes until golden brown.

9. 9. Let rest for 10 minutes before slicing and serving.