Substitute favorite aromatic for the scallion: onion, garlic, leek. Pair with vegetable being used.
Substitute favorite vegetable for the butternut squash, using up to 1-1/2 or 1-3/4 pounds for a thicker soup (I often do so with potato soup, using leeks for the aromatic).
Substitute half-and-half (use a whole pint if you want unless you have a use for the extra 1/2-cup) or other “milk”.
If you don’t have a stick blender, be VERY careful using a regular blender or food processor. If you don’t have any sort of blender, mince your aromatic as small as you can, use a potato masher to “blend” everything once the vegetables are cooked. It won’t be velvety smooth, but should still taste good.