I have canned butternut squash puree just chilling in my pantry. Could I try using it in this recipe?

Oh yes, you most certainly could- and to the point, you really should give it a go. Butternut squash risotto, with mushrooms of any sort, along with a salad, a slice or two of country style bread, and a glass of wine- YUM! If you have the wine, by all means use it- but if you don't, it's also good with all chicken broth.