Preheat the oven to 375F or 190C. Bring a Pot of salted water to boil. Add the Green Beans and cook for 1-2 minutes. Take them out and keep aside.
In a bowl, toss Panko Breadcrumbs with Olive Oil and Chopped onions. Mix and keep aside.
In a saucepan, whisk together cornstarch and 1 cup of milk. Whisk the remaining 2 cups of milk gradually. Add the Salt, Pepper, Ground Nutmeg, Ground Cloves, and Ground Cinnamon. As it comes to a slow boil, add the shredded cheddar cheese and mix well. Add the cheese, a handful at a time, wait for it to mix, and then add more. Whisk continuously. Stir in the Green Beans and mix it well with the white sauce.
Transfer this to a 3 Quart greased baking dish. Top with the crumbs and Parmesan cheese. Bake for 25-20 minutes, until the cheese is bubbling out and the top is golden brown in color.
Once baked, cut it into individual servings and enjoy