Preheat the oven to 350°F. Lightly grease a 9x13-inch casserole dish.
In the bowl of a blender, combine the drained and rinsed cashews, 2 cups broth, tamari, vinegar or lemon juice, salt and pepper. Blend until a smooth creamy sauce forms. Taste test to see if you prefer more acidity (vinegar or lemon juice) or more salt. Set aside.
Next, cut your green beans in half (this step isn't exactly necessary but it does make them easier to eat). Place the green beans in a large steamer basket and steam for about 7-10 minutes, just until they barely tender. Rinse with cold water until the green beans are completely cooled then set aside.
Meanwhile, warm the olive oil in a large pot over medium heat. Add the shallot and cook for 3 minutes. Add mushrooms and garlic and cook just until the liquid from the mushrooms begin to release, for about 5 minutes more.
To the pot, pour in the cashew cream from the blender. Bring to a low boil and simmer for 3 minutes, until the cream begins to thicken slightly. Add the green beans to the pot and stir until evenly coated.
Transfer the green beans and the sauce from the pot to the greased baking dish. Top with crisp onions then cover with foil or a lid (I just use parchment paper)and bake for 30 minutes. Allow to cool for a few minutes then serve warm and enjoy!