Lighter Baked Mac and Cheese

I got this recipe here, but I modified it some.

24 oz high fiber elbow pasta
2 tbsp light butter
1/4 cup flour
3 cloves garlic, minced (could use a tad more)
1/4 cup onion, minced
2 cups low fat milk
1 cup fat free chicken broth
8oz reduced fat sharp cheddar cheese
sea salt and pepper to taste (I started with 1/4 tsp pepper and 1/8 tsp salt)
2 cups fresh spinach
Handful of shredded parmesan cheese
Handful of shredded sharp cheese
Handful of seasoned whole wheat breadcrumbs

Preheat oven to 375 degrees. Cook pasta in salted water. Melt the butter in a large saucepan on low heat. Add onion and garlic and stir for about two minutes. Add flour and whisk until thick. Add chicken stock and milk. Turn heat to medium and cook until bubbling. Add salt and pepper. Remove from heat and add sharp cheese. Stir until melted and well blended. Adjust salt and pepper if needed.

Transfer pasta to a baking pan. If you want the breadcrumbs to be golden brown then make sure the pan is broiler safe. I did not check that  Add cheese sauce and stir. Add spinach and combine thoroughly. Top with parmesan and sharp cheese first then breadcrumbs. Cook for about 15-20 minutes or until cheese has melted. Place pan in broiler to get the breadcrumbs crispy.