Meanwhile, trim the edges of the beans and cut them into two pieces. Chopping beans are optional. As my casserole dish doesn't fit the long beans, I chopped them.
When the water boils, add the salt and chopped beans and reduce the heat.
Let the beans cook for five minutes.
After 5 minutes, drain the water and run the beans under cold water or add ice cubes. We need crunchy green beans. So adding the cold water stops the cooking process and also retains green color.
Set this aside.
Preparing Sauteed Onion and Mushrooms
Chop the onion, mushroom, and garlic.
Heat a pan or skillet and add butter.
Once the butter melts, add the onion, mushroom, salt, and garlic.
Saute over low heat for 15 minutes or until the mushrooms and onion are tender and caramelized like below.
Let it cool until you prepare the white sauce.
Preparing White Sauce
In a large pan heat 1 tbsp butter.
Then add the APF and whisk it immediately and ensure there are no lumps.
Then add two cups of milk and stir it.
Reduce the heat to low and keep stirring the milk for a couple of minutes.
Then add all the dried herbs and cream. Mix well again.
Let the milk reduce to half or until your desired consistency.
Turn off the heat and let it cool.
Assembling and Baking the Green Bean Casserole
Grease the casserole dish with oil or butter.
Preheat the oven to 350 deg F.
Spread the sauteed mushrooms and onions evenly in the casserole dish.
Then arrange the beans evenly.
Finally, pour the white sauce on top followed by panko breadcrumbs and cheese.
Bake this for 16 minutes or until the cheese melts and the panko browns up.
Serve it hot with crushed black pepper with other Thanksgiving recipes.
Notes
As I mentioned above, if you want to keep semi-homemade, you can use store bought cream of mushroom soup and use it instead of white sauce.
Also, I have seen french fried onions in the baking aisle. If you buy store bought ones, you can use instead of sauteed onion, or you can prepare homemade fried onions like pakoras.
Adjust the amount of salt and dried herbs as per your preference.
I added the black pepper only before serving. But you can add required black pepper while cooking the mushrooms, white sauce or layering too.
Instead of black pepper, you can serve this with crushed red chili flakes too.