Preheat your oven to 350˚F.
Cook the lasagna noodles according to package directions until al dente. Drain and set aside.
Place the baby spinach in a microwave-safe bowl and heat in increments of 30 seconds until it begins to wilt. Set aside.
In a large saucepan, melt the butter over medium heat. Stir in the flour to create a roux, then gradually whisk in the milk until the sauce thickens. Add garlic, salt, and pepper.
Layer the ingredients in a baking dish starting with white sauce, followed by noodles, ricotta, wilted spinach, mozzarella, and more sauce. Repeat until all ingredients are used, finishing with sauce on top.
Cover with foil and bake for about 25 minutes. Remove foil and bake for an additional 15 minutes until bubbly and golden brown.
Let the lasagna cool slightly before serving and garnish with chopped parsley.