Cello mushrooms are fresh, sliced mushrooms packaged for convenience. They have a mild, earthy flavor and are perfect for adding to stir-fries, salads, or soups, enhancing dishes with their savory taste. are fresh, sliced mushrooms packaged for convenience. They have a mild, earthy flavor and are perfect for adding to stir-fries, salads, or soups, enhancing dishes with their savory taste.