• Preheat oven to 350 degrees F. Spray a 9x13-inch baking dish with non-stick cooking spray and set aside.

For the Onion Topping:

• Next to the onion slices, set up your assembly line: Into a medium-size mixing bowl, add the plant milk. Soak onion slices in the milk for 5 minutes.
• In a second medium-size mixing bowl, stir together the all-purpose flour, garlic powder, onion powder, sea salt, and ground black pepper.
• Add a handful of onions to the flour mixture and toss gently to coat. Remove to a plate and repeat with the remaining onions, working in batches until all onion slices are coated.
• Into a large skillet over medium-high heat, add the vegetable oil. When the oil is hot, work again in batches adding a handful of onions each time. Allow onions to cook mostly undisturbed, stirring only as needed until golden brown. Move cooked onions onto a paper towel-lined plate to drain. Season lightly with salt, to taste. Set aside.

For the Casserole:

• Set a large pot on the stove top over medium heat and add the butter. When the butter is melted, whisk in the flour, thyme, salt, garlic powder, onion powder, and black pepper and remove from heat.
• Stir in 1/2 cup of cheddar cheese and all of the sour cream until sour cream iis smooth. Add the green beans and half of the onions, then toss to coat thoroughly.  Adjust seasoning to taste.
• Transfer the green bean mixture to the prepared baking dish. Sprinkle with the remaining 1/2 cup of cheese and the remaining onions. Bake for 25-30 minutes, until heated through. Serve hot.