Christmas baking?

Whatever made me think that I could bake? The children wanted me to make shortbread. I found that the Nova Scotia Tea Room and Emporium made good shortbread. I bought it. But I have a guest arriving that needs gluten free stuff, and I found this recipe that used either corn starch or potato flour. I had corn starch. They were supposed to be thumb cookies - bake for around 15 minutes - here is the result after seven and a half minutes. Melted and spread. I wonder what would happen if I used potato flour? Why don't I just accept that the Universe has conspired against me ever baking?