Cover cashews with water and refrigerate overnight.
Drain cashews and place in a blender. Add water, coconut aminos, salt, onion powder, and garlic powder. Blend until smooth and creamy.
Place green beans in boiling water. Cook 3 minutes, transfer immediately to an ice bath to cool. Remove from ice water to pan lined with towels. Blot dry.
Heat oven to 350° Grease a 3-quart casserole dish with ghee or avocado oil; set aside.
In a large skillet over medium heat melt ghee. Add mushrooms and cook until browned.
In a large bowl combine cashew cream, green beans, and mushrooms. Stir to thoroughly combine. Transfer to prepared pan.
Bake 20-25 minutes until hot and beans are tender.
Meanwhile, toss onion slices with arrowroot starch to coat.
Heat about 1-2-inches of avocado oil in a small saucepan over medium-high heat to 350°
Fry onions in batches, turning frequently, until crisp. Drain on a paper towel lined plate. Season with salt.
Top green beans with fried onions just before serving.