These are enoki mushrooms. They grow on the roots, branches, and tree trunks mostly in Japan. My mom and I typically use these in our soup-based meals such as udon or ramen.
This was my first time putting it in the udon I made this past week. You cut the roots off (the brown part). I usually cut it at the lowest point of the second tallest mushroom since they’re all different sizes. Separate the mushrooms from each other, then soak it in water for about 10 minutes to get it cleaned. Once you’re about to serve, just put it into the broth and then scoop it with the soup into the desired bowl. They don’t really need that much extra cooking. They have a unique crunch and flavor than other mushrooms.