Prepare the french fried onions (if using, see link) and the cream of mushroom soup (see the instructions below) and set aside. I prefer to make them both in advance. The cream of mushroom soup can be stored in the fridge for up to 2 days before assembling and the onions can be frozen up to 3 months.
Bring a large pot of water to a boil and lightly season with salt.
Cut the ends off the green beans, then, cut them in half for shorter pieces. Drop them into the boiling water. Boil until they reach your desired tenderness, about 4 or 8 minutes. They will continue to cook in the oven but not much. Immediately drain the green beans and rinse in cold water to stop the cooking process. Return to pot and set aside.
Preheat the oven to 375 degrees.
Dice the onion and bacon.
Heat a small skillet over medium heat and add the bacon. Cook until the bacon is crispy, 3 to 5 minutes. Add the onion and garlic. Continue cooking until the onion is transparent, another 3 to 5 minutes.
Add the pimentos, lemon juice, and cream of mushroom soup to the bacon/onion mixture. Taste and add salt and pepper as needed (if it tastes "flat", it needs salt!). Stir to combine. Pour over green beans and stir gently to combine.
Pour into glass or ceramic 3-qt casserole dish.
Crumble the almond flour topping over the casserole (instructions below) OR sprinkle with shredded shredder cheese.
Place in the oven for 25 minutes.
Turn the oven to broil, then if you would like an added crunch, optionally top with either french fried onions or crushed parmesan crisps. Cook until the top starts to brown, about 3 - 5 minutes. If the fried onions have been frozen, it may take longer. Watch the topping carefully so it doesn't burn.
Cream of Mushroom Soup:
Heat the butter or oil in a medium-sized saucepan over medium heat.
Once hot, add the onion, garlic, and mushrooms. Sautee until the mushrooms are soft and the onion is translucent.
Slowly add in the chicken broth and heavy cream. Then stir in the thyme, cayenne (if using), salt, and pepper. Taste and adjust seasonings as needed. Allow to bubble around a minute then remove from heat.
Transfer to a blender and blend until smooth (or use an immersion blender). Be very careful because the soup is hot!!! If you prefer some texture, reserve some mushrooms and stir in after blending.
Optional Almond Flour Topping:
In a small bowl, whisk together the dry ingredients. Stir in the avocado oil until crumbly.
Notes
Nutritional Information uses the almond flour topping without fried onions or parmesan crisps.
This casserole dish can be made and assembled in advance. Just prepare the dish through step 9 then cover and leave in the refrigerator until ready to bake, up to 2 days.
I only recommend freezing the fried onions because they will get soggy when stored at room temperature or in the fridge. Then, when ready to use, just add the frozen fried onions to the top of the casserole - no need to thaw!
The casserole can be topped with the almond flour mixture or shredded cheese. Then, if you would like some added crunch, top with french fried onions or parmesan crisps toward the end of baking.
Please don't use frozen green beans! Frozen green beans tend to taste waxy and get soggy. While nothing is as good as fresh green beans, most supermarkets sell refrigerated fresh-cut green beans. They are found in the produce section and are a close second.