Bring a large stock pot of water to a rolling boil. Cook green beans for 3-4 minutes and transfer into a large bowl filled with ice water. This will stop the cooking process of the beans. Once cooled, drain and transfer beans to a separate large bowl.
In a large sauté pan, melt butter on medium heat. Add in sliced mushrooms and cook for 5-10 minutes or until mushrooms are golden brown. Add in minced garlic and cook for 1-2 minutes or until fragrant.
In a large bowl, stir together the soup, half and half, black pepper, soy sauce and ½ of the crispy fried onions.
Combine the soup mixture and green beans together. Transfer mixture to a large casserole dish. Cover with foil and bake for 20 minutes. Remove foil, top with remaining onions and bake for an additional 5-10 minutes or until bubbly and golden brown.
Note*If making the recipe the night before, make up until step 4, cover with plastic wrap and wait to add the crunch onions until just before baking.