Cover the rice with boiling water and let sit for at least 10 minutes, up to 3 hours. (see note) Rinse and drain.
Bring the milk and water to a boil in a pressure cooker pot. (See notes for stovetop cooking.)
Add the soaked rice, dates, cinnamon stick, and salt. Lock the lid in place and bring to high pressure for 20 minutes. Use a natural pressure release.
When the pressure has released, stir in the pumpkin puree, maple syrup, and pumpkin spice mix. Cook, stirring constantly for 3 to 5 minutes. Remove from the heat and stir in the vanilla. Discard the cinnamon stick.
Transfer to a bowl and cover the surface with plastic wrap, so it touches the hot pudding, to prevent a skin from forming, and so the steam from the hot pudding doesn’t condense and create water on the surface. Let cool about 30 minutes. The pudding will thicken as it cools.
Spoon into serving cups. Serve warm, or cold, with fresh whipped cream. Keep it vegan by topping with coconut cashew whipped cream. Sprinkle with pumpkin spice mix.