This homemade healthy keto green bean casserole recipe features fresh green beans baked in a creamy, dairy-free mushroom sauce, topped with homemade crispy fried onions. A healthy twist on a classic holiday favorite! 

This post was originally published on Oct 17, 2019 and updated with new copy on November 4, 2021!

keto green bean casserole topped with homemade french fried onions in a white baking dish

Green Bean Casserole is one of my all-time favorite side dishes, and I’ve really missed it since having to go gluten-free and dairy-free. The traditional version of this is made with Campbell’s Cream of Mushroom Soup, which is definitely not on the list of things that I can eat anymore. It’s loaded with canola oil, soy, wheat, corn starch, and MSG. I wanted to create a healthy version of my favorite Thanksgiving side dish that tastes close enough to the original, but doesn’t have any of the bad stuff! Now you can add this incredible low carb green bean casserole to your holiday recipe rotation!

If you’re used to making Keto recipes, you may have seen green bean casserole dishes made with crushed pork rinds and cream cheese, but for this recipe, I chose to make my own gluten-free crispy fried onions and used dairy alternatives. You won’t even tell the difference!

What Makes This Recipe Work

Green bean casserole is a holiday classic for a few reasons. How could anyone not love green beans baked in a creamy mushroom gravy-like sauce, then topped with french fried onions? It’s cozy comfort food at its finest. But for me, I want to enjoy all the delicious holiday food without feeling terrible afterward. Nowadays, making healthy, low-carb hacks is easier than ever. And this green bean casserole is no exception. Keto, and free of so many common allergens, this casserole is a side dish everyone can (and will) love!

a close up of a low carb side dish for Thanksgiving made with grean beans, mushroom sauce, and crispy fried onions in a white casserole dish.

Ingredient Notes

Mushroom sauce: I make the creamy, low carb mushroom sauce for the green beans using a combination of full fat coconut milk and cashews. It’s important to stir the coconut milk before measuring, as it can separate in the can. I also use Sherry cooking wine in this recipe because it gives it an incredible flavor. If you’re doing a Whole30, just omit this ingredient! It will still be super tasty.

Tapioca Flour: To fry the onions that go on top of the green bean casserole, but still keep it Keto, I use a combination of ghee + avocado oil. I also dipped them in egg and then a mixture of tapioca flour, coconut flour, and spices.

Fried Onions: I decided to go the extra mile and fry my own onions for the topping! It is a little labor-intensive, but they are SO delicious! If you don’t have time to (or don’t want to) make your own, I know that Whole Foods has gluten-free Crispy Onions as an option. A reader also mentioned that Aldi has a GF Fried Onion option, too! If you’re not worried about Whole30, you can save time and use store-bought fried onions.

green beans mixed with a creamy, low carb, dairy free mushroom sauce and baked with crispy fried onions in a white casserole dish.

Mary’s Tips & Tricks

Storage: If you have leftovers, store them in an airtight container for 3-5 days in the fridge, 10-12 months in the freezer!

Thrive Market: If you are new to the Keto/Paleo lifestyle or don’t have a ton of these pantry staples on hand, Thrive Market is an amazing place to get them. They sell healthier items for cheaper than retail prices. You can use this link to get 25% off your first order! Everything linked above will also get you the 25% off.

FAQs

Can I make this casserole side dish ahead of time? Yes! You can combine the green beans and the mushroom sauce the day before. Store in an airtight container in the refrigerator and bring it to room temperature before adding the onions and baking!

Do you have to soak the raw cashews first like in some recipes? No! You don’t need to soak the cashews.

Is there a way to make this green bean casserole nut-free? I haven’t tested it without cashews, however, you could try all coconut milk and thicken the sauce with arrowroot powder mixed with water: 1 tbsp arrowroot in 3 tbsp water. Use a little at a time until it thickens to your liking.

Other Healthy Holiday Side Dishes

Creamy Dairy Free Mashed Potatoes

Bacon Maple Brussels Sprouts with Pecans and Cranberries

Gluten Free Dairy Free Sausage Apple Herb Stuffing

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Keto Green Bean Casserole

This easy, keto casserole recipe features fresh green beans baked in a creamy, dairy-free mushroom sauce, topped with homemade crispy fried onions. A healthy twist on a classic holiday favorite! Whole30, Gluten Free, Paleo, & Low Carb
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Ingredients

  • 2 lbs green beans, ends chopped
  • 8 oz cremini mushrooms, chopped
  • ½ large onion, diced
  • 3 cloves garlic, minced
  • 1 tbsp ghee
  • 1 tbsp sherry, omit for Whole30
  • 1 cup chicken broth
  • 1 tsp dried thyme
  • 1 tsp sea salt, more to taste
  • ½ cup full fat coconut milk, stirred before measuring - it separates in the can
  • ½ cup raw unsalted cashews
  • 1 tbsp fresh squeezed lemon juice
  • ½ cup water

Homemade Fried Onions

  • 1 large onion, sliced in half and then cut into 2-3 inch pieces
  • 2 tbsp ghee
  • 2 tbsp avocado oil or coconut oil
  • 2 eggs, beaten
  • 2 tbsp tapioca flour
  • ¼ cup coconut flour or fine almond flour
  • 1 tsp garlic powder
  • ½ tsp sea salt
  • ½ tsp paprika

Instructions
 

  • Preheat oven to 375. Grease a 9x13 in casserole dish. Fill a large pot with water and bring to a boil. Add the green beans and boil for 5 minutes until crisp tender. Drain and set aside.
  • Heat up the tbsp of ghee in a large skillet. Add in diced onion, garlic, and mushrooms. Sprinkle with a bit of salt and pepper. Saute and let them cook for 7-8 minutes, stirring occasionally, until the mushrooms have sweat off some of their liquid. Add in the sherry (if using) and use a spoon to scrape the brown bits from the bottom of the pan. Add in the chicken broth, thyme, and sea salt. Bring to a boil, then reduce heat to medium low. Let it simmer while you make the coconut cashew cream.
  • Combine the coconut milk, cashews, lemon juice, and 1/2 cup of water in a blender. Blend on high for 1 minute until very thick and creamy.
  • Pour the cream into the pan and stir for 1-2 minutes. It should thicken fairly quickly. Taste it to see if you want to add more salt. You can use the sauce as-is, or use an immersion blender to break down the mushrooms a bit. It is up to you!
  • Add green beans to the casserole dish and pour the mushroom sauce on top. Stir to combine. Bake for 20 minutes.
  • Make the fried onions (if not using store-bought): Beat eggs in a shallow dish. Add tapioca flour, coconut (or almond) flour, garlic powder, salt, and paprika to a separate shallow dish and stir to combine. Heat the ghee + cooking oil in a large skillet over medium heat. Dip the onion pieces into the egg, and then into the flour mixture to coat. Fry them for 2-3 minutes each side or until they are browned to your liking. Transfer to a paper towel-lined plate to drain. Work in batches until all onion pieces have been fried.
  • When the timer goes off, add the fried onions to the top of the casserole (you may have some leftover - but they make a yummy snack!), and cook for an additional 10 minutes. Serve and devour!

Notes

If you're not worried about Whole30, you can save time and use store-bought fried onions. If gluten free, Check Whole Foods for their 365 brand Gluten Free Crispy Onions! Aldi also has a GF version, as well. 

Nutrition

Calories: 247kcal, Carbohydrates: 19g, Protein: 7g, Fat: 18g, Saturated Fat: 8g, Polyunsaturated Fat: 2g, Monounsaturated Fat: 7g, Trans Fat: 1g, Cholesterol: 55mg, Sodium: 581mg, Potassium: 534mg, Fiber: 5g, Sugar: 6g, Vitamin A: 857IU, Vitamin C: 19mg, Calcium: 71mg, Iron: 3mg