Blanch Green Beans: Fill a medium saucepan ¾ full of water and bring to a simmer. Meanwhile, take a large bowl and fill ¾ of the way with water. Add ice to create an ice bath. Set aside. Add 1 pound fresh green beans to the simmering water. Let cook 2-4 minutes. Using a pair of tongs, carefully remove the green beans from the simmering water and place them directly into the ice bath. Let sit for 5 minutes or until fully cooled. Remove and place into a 9x13 baking pan.
Cook Onions + Mushrooms: Bring cast iron skillet to medium-high heat. Add 3 tablespoons of butter and let melt; swirl to coat the pan. Add onion and 1 teaspoon garlic. Move around pan until until the onions have softened, approximately 2-3 minutes. Add 12 ounces baby bella mushrooms and move around pan until they have softened, another 2-3 minutes. Remove mushrooms and onions with slotted spoon and place on a plate. Set aside.
Make Sauce: Add remaining 4 tablespoons of butter to pan and let melt. Add 3 ½ tablespoons gluten-free 1-to-1 baking flour and use a whisk to combine into a paste (a.k.a. a ). Slowly add 1 ½ cups Nutpods unsweetened/unflavored creamer and then ¾ cup chicken broth, whisking the entire time and ensuring the mixture is hot enough to just barely simmer. Let simmer, uncovered, 3-5 minutes. Once thickened remove from heat and add back in the mushrooms and onions as well as 1 teaspoon kosher salt, ¼ teaspoon ground black pepper and ¼ teaspoon red pepper flakes (if using). Stir to combine. Taste and adjust salt or pepper, as needed.
Combine: Pour the mushroom mixture over the green beans and add approx. 3/4 cup of the gluten free french fried onions; stir to combine.
Bake: Place in oven, middle rack and uncovered, for 20-25 minutes. Remove and cover with remaining gluten-free french fried onions. Return to oven for an additional 5-10 minutes.
Cook + Serve: Remove and let cool sightly before serving (sauce will thicken as it cools).