In a skillet, melt butter and cook onions for 2 minutes. Add mushrooms and cook until golden. Stir in soup and cream. Bring to a simmer. Stir in the cheddar cheese. Season with salt and pepper. Stir in green beans and toss to coat. Transfer to a buttered casserole. Top with fried onions and bake for 30 minutes or until bubbly.
Recipe Courtesy of Food Network Kitchens