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Gluten Free Green Bean Casserole

Gluten free green bean casserole combines tender green beans and a creamy mushroom sauce with homemade crispy fried onions. Bake it in a 9x13-inch dish until bubbling, then finish with a crisp, golden topping.
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Prep Time 20 minutes
Cook Time 55 minutes
Resting time 5 minutes
Total Time 1 hour 20 minutes
Servings: 8 servings
Course: Side Dish
Cuisine: American
Calories: 310
Ingredients Equipment Method Notes

Ingredients
  

For the crispy onions
  • 1 yellow onion large, very thinly sliced
  • 0.5 cup rice flour
  • 1.5 tsp kosher salt divided
  • 3 cup canola or vegetable oil for frying
For the casserole
  • 2 lb fresh green beans trimmed and cut into 2-inch pieces
  • 4 tbsp unsalted butter
  • 8 oz cremini mushrooms sliced
  • 2 cloves garlic minced
  • 0.25 cup gluten-free all-purpose flour
  • 1 cup gluten-free chicken broth
  • 2 cup whole milk
  • 0.5 tsp black pepper

Equipment

  • 1 heavy 3-quart saucepan
  • 1 9x13-inch baking dish
  • 1 large skillet

Method
 

Fry the onions
  1. Toss the onion slices with the rice flour and 1/2 teaspoon of the salt, separating the slices into rings and shaking off excess flour.
  2. Heat the oil in a heavy 3-quart saucepan to 350°F.
  3. Fry the onions in small batches for 2 to 3 minutes per batch, turning once, until crisp and golden.
  4. Drain the onions on a wire rack and season with the remaining 1/2 teaspoon salt.
Make and bake the casserole
  1. Heat the oven to 375°F.
  2. Grease a 9x13-inch baking dish.
  3. Bring a large pot of water to a boil, add the green beans, and cook for 4 minutes.
  4. Drain the green beans and rinse under cold water.
  5. Melt the butter in a large skillet over medium heat, add the mushrooms, and cook for 6 to 8 minutes, stirring occasionally, until softened and their liquid has evaporated.
  6. Stir in the garlic and cook for 30 seconds.
  7. Sprinkle in the gluten-free flour and cook for 1 minute, stirring constantly.
  8. Gradually whisk in the chicken broth and milk, then cook for 4 to 6 minutes, stirring, until the sauce thickens enough to coat a spoon.
  9. Stir in the remaining 1 teaspoon salt and the black pepper.
  10. Stir the green beans into the sauce and transfer the mixture to the prepared baking dish.
  11. Bake for 20 minutes, until bubbling around the edges.
  12. Scatter the crispy onions over the casserole and bake for 8 to 10 minutes, until the topping is hot and crisp.
  13. Let the casserole rest for 5 minutes before serving.

Notes

Fry the onions in small batches so they crisp evenly. Store leftovers covered in the refrigerator for up to 4 days; freezing is not recommended because the topping loses its crispness. For a dairy-free swap, use plant-based butter and unsweetened, unflavored dairy-free milk.