Preheat the oven to 220°C/200°C fan/425°F/gas mark 7. Line two baking sheets with baking parchment.
Place the flour in a large bowl along with the baking powder, bicarbonate of soda, pumpkin spice, salt and sugar and mix to combine.
Add the cold, cubed butter and rub in using your fingertips until the mixture resembles fine breadcrumbs and no lumps of fat remain.
Mix the pumpkin puree with the vinegar and vanilla and add it to the bowl with the non-dairy milk.
Stir to form a soft, sticky dough. If it is too dry add a drop more milk.
With well floured hands, divide the dough into two equal pieces and shape each one into a rough ball.
On a floured surface, pat each ball of dough out into a round about 4cm / 1 ½ inches thick.
Use a sharp knife dipped in flour to slice each round into six triangles. Dip the knife in flour between cuts to prevent it from sticking.
Gently place the wedges well spaced apart on the baking sheets. They will probably be a bit soft and delicate so it is a good idea to use a floured spatula or fish slice to help move them. If they get a bit squished out of shape you can gently pat them back into shape using floured hands once they are on the baking sheet.
Gently brush the tops of the scones with milk. Bake for about 12 minutes until well risen, golden and firm to the touch.
While the scones are baking make the glaze. Place the butter and maple syrup in a small pan and heat gently until the butter is melted.
Whisk in the icing sugar and a pinch of salt. Set aside to cool, the glaze will thicken as it cools. If it is still too runny then you can whisk in more icing sugar to thicken it.
Once the scones are baked, drizzle them with the glaze and serve as soon as possible.