Combine the onions with the salt and the buttermilk. Let them sit for 5-10 minutes.
2 medium onions, ½ cup buttermilk, 1 tsp kosher salt
In a large shallow dish, combine the flour and the panko bread crumbs and toss to combine. Add in the onion rings a little at a time. Toss to coat with the breading mixture and then set them on the baking sheet until you cook them.
¼ cup all-purpose flour, ¼ cup bread crumbs
Spray a thin coat of spray on the onion rings.
cooking oil spray
Place the pan on the middle rack of the oven and bake until golden brown, approximately 20 minutes.
Watch closely as oven temperatures vary. Toss the onions 2 to 3 times during cooking.
Once done, remove from the oven and set aside until ready to use. Turn the oven down to 400℉.
Blanch the green beans
While the onions are cooking, prepare the beans.
Bring the water and 2 tablespoons of salt to a boil in an 8-quart saucepan.
10 cups water, 2 tablespoons kosher salt
Add the beans and blanch for 5 minutes.
1 pound haricots verts
Drain in a colander and immediately plunge the beans into a large bowl of ice water to stop the cooking. Once they thoroughly cooled, drain off the water and set aside.
10 cups ice water
Creamy Mushroom Sauce
Heat the butter and olive oil in a large heavy-bottomed skillet set over medium-high heat. Add the sliced mushrooms and 1 teaspoon salt. Cook, occasionally stirring, until the mushrooms are a deep golden brown, approximately 10 minutes.
Stir in the garlic and cook for another 1 to 2 minutes—season with black pepper. Adjust the salt if needed.
2 cloves garlic, 1/2 teaspoon freshly ground black pepper
Sprinkle the flour over the mixture and stir to combine. Cook for 2 to 3 minutes. You want to cook the flour and brown it slightly.
2 tablespoons all-purpose flour
Add the broth, stir and simmer. The flour and broth will combine to thicken the sauce.
1 cup chicken broth
Decrease the heat to medium-low and add the half-and-half. Cook until the mixture thickens, stirring occasionally, approximately 6 to 8 minutes.
1 cup half-and-half
Finish the sauce with a sprinkle of fresh thyme.
1 teaspoon fresh thyme
Remove the mushroom mixture from the heat and stir in 1/4 of the onion rings. Stir to combine.
Assemble The Green Bean Casserole
Combine the green beans and the creamy mushroom sauce. This can be done by adding the green beans to the mushroom sauce and then adding the mixture to your baking dish. OR The green beans can be added to the dish and then the mushroom sauce poured over the beans.
Top with the remaining onion rings. (Right before baking.)
Bake @ 400℉. Place the casserole into the oven and bake until bubbly, approximately 20 to 30 minutes. Remove and serve immediately.
Video
RECIPE TIPS
SubstitutionsGluten-free: Use gluten-free flour and bread crumbs. Dairy-free: Use a dairy-free creamer instead of half and half, OR use a simple cashew sauce. Make-ahead InstructionsYou can easily make the mushroom cream sauce and even blanch the green beans several days ahead. If you want to make sure the onion rings are crispy, it is best to make them the same day.
Follow the instructions for the mushroom cream sauce with the exception of adding the onion rings. Store in an airtight container.
Blanch the green beans and refrigerate until you are ready to bake.
Simple Cashew Sauce
1 cup of raw cashews
3 cups of water (to soak overnight)
2 cloves of garlic
a few pinches of salt
How to make the cashew sauce
Soak the cashews overnight in water.
Drain, and then add the cashews, garlic, and salt to a high-speed blender.
Turn the blender on and begin to add fresh water until the sauce is the consistency of a thin pancake batter. You will use 1 to 2 cups of water.