1. Preheat oven to 375F / 190C and have a medium size casserole dish ready.
2. Place a medium sized pot over medium-low heat. Add onion, mushrooms, garlic and non-dairy butter or oil, and sauté until the onions and mushrooms have softened.
3. Next add the all-purpose flour and a pinch of salt and pepper, stir through to coat the mushrooms and onions, continue cooking this mix for about two minutes (this step removes the “raw” taste of the flour).
4. Slowly pour the almond milk into the pot. At the same time, stir the mixture continuously. When done carefully, this will make sure your gravy is smooth, not lumpy. Add the steamed green beans and mix through the mushroom gravy to coat the beans. Have a taste and add a little more salt and pepper, if needed. (See notes for making this dish ahead of time/meal prepping). 
5. Transfer the green beans and gravy mixture to a casserole dish. Top with shredded non-dairy cheese and bake until cheese has melted, about 10-15 minutes.
6. Remove the green bean casserole from the oven and sprinkle with crispy fried onions. Serve immediately while hot! Enjoy!

Store any leftovers in an air-tight container in the refrigerator and consume within 3 days.