Green Bean Casserole (Gluten-Free)
Created by Campbell's in 1955, the original recipe uses canned green beans and canned cream of mushroom soup.  
To make Thanksgiving prep a little easier, you can make the casserole the night before. (Don't top it with the fried onions the night before or they'll get soggy.) About 30 minutes before you are ready to serve, heat the casserole in the oven and then top with the freshly fried onions.

Ingredients
For the Fried Onions

• 3 tablespoons cornstarch
  
• 3 tablespoons white rice flour
  
• 1 medium onion, sliced into thin strips
  
•  Vegetable oil for frying
  
• Salt, to taste
  

For the Casserole

• 3 tablespoons olive oil, divided
  
• 1 small onion, finely diced
  
• 8 ounces white button mushrooms, finely chopped (approximately 3 cups) 
  
• 1 clove garlic, minced or put through a garlic press
  
• 2 cups milk, divided
  
• 2 tablespoons cornstarch
  
• 1 (16-ounce) bag frozen French-cut green beans, thawed and drained or 16- ounces fresh green beans, cleaned, trimmed, and cooked until tender
  
• 1/8 teaspoon ground thyme
  
• Salt and pepper, to taste
  
• 1/4 cup grated Parmesan cheese, divided 
  

Procedures

1. For the Onions: In a large zip-closebag, combine cornstarch and white rice flour. Add onions and shake bag to combine. Remove onions from bag; shake off any excess flour. 
   
2. Fill a large heavy-bottomed skillet with 1/2 inch of vegetable oil. Heat oil over medium-high heat until hot and shimmering. (To test your oil, drop one onion slice into it. The onion should sizzle when it hits the oil. If it doesn't, the oil is not hot enough.) Fry a handful of onions, about 4- 5 batches, until golden brown and crispy. 
   
3. Remove onions from oil using a slotted spoon. Place on paper towel to drain. If desired, season with salt to taste. Repeat with remaining onions. 
   
4. For the casserole: Preheat oven to 350F. In a medium saucepan, heat 2 tablespoons of olive oil over medium-high until shimmering. Add onion and garlic. Sauté until soft, stirring frequently. Add mushrooms and remaining tablespoon of olive oil. Cook until mushrooms are soft and tender, stirring frequently, about three minutes. 
   
5. Add 1 3/4 cups of milk and thyme. Bring to a boil. Once the mixture boils, combine remaining 1/4 cup of milk and two tablespoons cornstarch. Stir vigorously with a fork to combine milk and cornstarch. Quickly whisk in cornstarch. Allow to boil for 45 seconds. Remove from heat. Reduce heat to low. Allow to simmer for three minutes. Salt and pepper to taste. 
   
6. Add green beans, stir to combine. Pour into a 1 1/2-quart casserole dish. Top with half the grated Parmesan cheese. Cover with foil. Bake for 30 minutes. 
   
7. Remove foil. Sprinkle fried onions and remaining cheese over the top of casserole. Return to oven until bubbling and lightly golden brown, about seven minutes. 

11/16/2014 Gluten-Free Green Bean Casserole | Serious Eats : Recipes