We used frozen organic butternut squash. You can use fresh, you just need to adjust the recipe to allow for baking, cooling, peeling, cleaning and cutting the squash.
If you don’t have an immersion blender, get one. It’s safer and easier than transferring it in batches to and from a blender. You can find them just about anywhere for around $30. If you have to use a blender, make sure you use one with a glass pitcher and handle very carefully. Make sure the lid is tight and cover it with a towel. After you see how easy this is to make, you will want to make it more often and will appreciate the immersion blender. They come in handy for making creamed soups and sauces.