Make French fried onions or use store bought. Set aside.
Bring a large pot of water to a boil. Add green beans. Blanch for 3-4 minutes. Drain. Set aside.
Melt butter in a large frying pan over medium-high heat.
Add onions. Sauté for 2-3 minutes or until soft.
Add mushroom soup, milk, garlic powder, cayenne pepper and dried thyme. Stir to combine. Season with salt and pepper.
Cook, stirring occasionally, for about 3 minutes.
Stir in green beans. Remove from heat.
Add 1 cup French fried onions. Stir to combine.
Transfer the mixture to a 9 x 13 - inch casserole dish or baking pan.
Store this in the refrigerator overnight or cook straight away.
Preheat oven to 200 C / 400 F.
Cover the casserole dish with aluminum foil, and bake for about 20 minutes.
Remove foil.
Top with the remaining French fried onions and bake for another 10 minutes.
Serve as Thanksgiving side.