Preheat oven to 350 degrees.
In a medium saucepan, melt butter. Add flour and whisk together until a light brown roux forms. Cook the roux over medium heat until roux is golden. This will also help remove that "flour-y" taste.
Slowly add chicken broth and bring to a low boil whisking constantly. Stir in 1 cup of full fat milk.
Add diced and drained tomatoes, green chile peppers, and shredded cooked chicken, stirring to combine and heat, approximately 5 minutes. Remove from heat and set aside.
In a medium mixing bowl, blend together ricotta cheese, eggs and shredded cheddar and mozzarella cheeses.
Coat a 3 quart lasagna pan with cooking spray.
Place a 1/3 of the sauce on the bottom. Top with 4 lasagna noodles and then ricotta and cheddar cheese mixture.
Repeat 3 times, with last layer being cheese mixture. Sprinke the Cotija cheese over the top of the lasagna.
Cover with aluminum foil and bake for 45 minutes. Remove foil and cook an additional 15 0- 20 minutes
Remove and allow to rest for 10 minutes. Top with fine chopped green onions for garnish.