Preheat the oven to 400F
In a large saucepan, bring the water to a boil and add the pasta
Cook for about 6 minutes then add the spinach
Cook for 2 minutes, until the spinach is wilted and pasta is cooked to al dente
Drain and place the pasta and spinach mixture in a large mixing bowl
Meanwhile, heat the oil in a large skillet over medium-high heat
Cut the chicken into bite-sized pieces and sprinkle with the onion powder, garlic powder, salt, and pepper then add to the pan
Cook for about 8 minutes or until the chicken is cooked through
Add the chicken to the pasta mixture
Lower the heat to medium and place the green onion in the warm pan
Cook for 2 minutes
Stir in the lemon zest and juice
Combine the milk, flour, and 1/4 cup of parmesan cheese in a bowl
Add the milk mixture to the pan and bring to a boil
Cook for 2 minutes or until the sauce has thickened
Add the milk mixture to the pasta mixture and toss to coat
Spoon the pasta mixture into a casserole dish and sprinkle with the remaining 1/4 cup of parmesan cheese, mozzarella cheese, and panko
Bake for about 8-10 minutes, until the panko starts to brown and cheese is melted