Prepare Pumpkin Purée according to this recipe preferably in the oven (or use canned pumpkin purée or another substitute, read the text above).
Heat the non-dairy milk along with the vegan butter in a pot until lukewarm. Transfer to a measuring jar. Add a tablespoon of the sugar, a tablespoon of the flour and the yeast and stir to combine. Rest in a warm place for around 10 minutes or until the yeast froths.
In a large mixing bowl combine the remaining flour, soy flour, remaining sugar, vanilla, cinnamon, and salt. Add pumpkin purée and gradually pour in the yeast mixture, and mix using a stand mixer with dough hooks (or a kitchen machine or simply knead with your hands) for about 6 to 8 minutes, or until a smooth sticky dough forms. If the dough is super sticky, add a little more flour.
Place the dough in a lightly greased bowl, cover, and place in a warm spot to rise until doubled in size, for about 1 hour.
Turn out the dough on to a floured surface and using a rolling pin roll it out to around 0.7-inch (1.5cm) thick.
Using a round cookie cutter or jar, cut out the doughnut rounds and place on a parchment-lined baking sheet, leaving space apart. Cover and let rise again until puffy, about 30 minutes.