Preheat oven to 350ºF. Lightly coat a baking dish with olive oil. Set aside.
Bring a medium pot of water to a boil and lightly salt. Add the green beans and boil for 1 minute. Pull the green beans out with tongs or a spider and drop into a bowl of ice water. Allow to rest for a couple minutes. Drain well.
Add the green beans, mushrooms, garlic, olive oil, parmesan cheese, and red pepper flakes to the prepared baking dish and toss to combine. Drizzle with heavy cream, season with salt and pepper and top with French fried onions.