When ready to fry the donuts, fill a dutch oven or heavy-bottomed pot with enough neutral oil to cover 2” (5 cm). Place the oil over low heat while the donuts rise.
Place a wire rack over a paper towel lined baking sheet. On a separate baking sheet, cut out 12 4” (10 cm) parchment squares for the donuts.
Cut 48 strings of kitchen twine about 12" long.
Divide the brioche into 12 equal parts. I recommend using a kitchen scale to get evenly sized donuts. Roll each part into a smooth ball, using small amounts of flour as needed.
Arrange 4 strings of kitchen twine in a star pattern and place one donut upside down in the center. Bring the opposite ends of each piece up around the dough and tie them to create eight sections. The twine should rest loosely against the dough, leaving room for it to expand as it proofs and fries. Cut the excess twine with kitchen scissors. Place the donut right side up on a parchment square and cover with plastic wrap while you finish the rest of the donuts.
Cover the donuts and allow to rise for about 1 hour or until puffy. When pressed with a finger, the dough will slowly spring back.
With about 30 minutes left of proof time, turn the heat up on the oil to medium and bring to 350 degrees F.
Meanwhile, make the cinnamon sugar. In a wide, shallow bowl, combine the sugar and cinnamon. Set aside.
Once the donuts have proofed, use the parchment squares to gently lower 3-4 donuts into the hot oil. Fry the donuts for 3 minutes on the first side, then flip over and fry for an additional 2-3 minutes until golden.
Transfer the donuts to the wire rack. Wait a couple of minutes for the oil to come back up to 350 degrees F (180 degrees C), then continue frying the donuts.
Once the donuts have cooled just enough to handle, cut the kitchen twine and gently peel off the donuts, then toss them in the cinnamon sugar to coat.
Once the donuts have fully cooled, fill each donut with the pumpkin cream and top with a pie crust leaf.