Combine the flour, sugar and pumpkin pie spice in a large bowl. Grate the butter into the flour and stir it in to coat evenly. In a separate bowl combine the pumpkin purée and buttermilk. Mix the wet ingredients with the dry ingredients, just until combined. Do not overmix. The dough should be quite wet.
Spread the all-purpose (not self-rising flour) out on a small cookie sheet. With a spoon, scoop evenly sized balls of dough into the flour, making sure they don’t touch each other. With floured hands, coat each dough ball with flour and toss them gently from hand to hand to shake off any excess flour. Place each floured dough ball into the prepared pan, right up next to the other. This will help the biscuits rise up, rather than spreading out. You might need to do the above in batches.