Preheat the oven to 350°F
In a large Dutch oven set the heat to medium-high heat and add 2 tablespoons oil, followed by garlic and onion. Sauté for 2-3 minutes.
Add seasonings (thyme, rosemary, oregano, bay leaf, salt, and pepper) followed by mushrooms. Continue sautéing until the onions and mushrooms are caramelized, about 5-7 minutes.
Drain and rinse cashews, then add them to your high-speed blender along with broth, nutritional yeast, lemon juice, soy sauce, salt, pepper, and half of your sautéed mushroom mix (don't forget to remove the bay leaf). Blend until smooth, adding more broth if neccessary.
Turn off the heat on the stovetop and add your blanched and trimmed green beans to the Dutch oven, followed by your soup mixture. Stir to combine everything.
Bake for 30 minutes, or until your green beans are fully cooked.
Remove your green bean casserole from the oven and top it with the fried onions. Bake for another 10 minutes.