Creamy Chicken Florentine Lasagna

tbsps unsalted butter

small onion, diced

garlic, minced

all-purpose flour

low sodium chicken broth

milk

dried basil

dried oregano

Salt and pepper,

lasagna noodles, cooked

skim ricotta cheese

cooked chicken breasts, shredded

baby spinach, roughly chopped

shredded skim mozzarella cheese, divided

grated Parmesan cheese, more for sprinkling on top