Make pasta ala dente according to the instructions and set aside. In a large sauté pan add the butter and place over medium heat. Next add the flour and whisk together with the butter until butter is completely melted. Once melted and blended, slowly add the milk and continue to whisk together. Let milk heat up to thicken slightly but don't burn. Then, add the mozzarella and cheddar cheeses and stir together.Finally, add the pasta back into the pan along with the spinach and the eggs. Stir well to coat the pasta and spinach and continue to cook until the some of the outer edges of the pasta begin to get crispy and the eggs cook through about 5-8 minutes. Remove from heat. Sprinkle bread crumbs over the top of the pasta and serve warm.