1. In a small bowl, stir the gelatin into 1/4 cup cold water and set aside.
2. Whisk the cream, milk, brown sugar, salt, vanilla extract or vanilla bean and cinnamon in a saucepan over medium heat until just beginning to boil.
3. Remove the pan from the heat and whisk in the softened gelatin. Add the pumpkin and whisk everything together, then strain through a fine-mesh sieve into a bowl or 2-quart liquid measure (this step is optional- I skipped it). Divide among 4-6 small jars or ramekins (I used teensy Weck jars). Refrigerate until firm to the touch, covering with plastic wrap once cool, at least four hours or overnight.
(If you make your panna cotta in ramekins: un mold each one by dipping the bottom of each ramekin in hot water for a few seconds. Next, run a small knife around the edge all the way to the bottom to loosen it. Cover with a dessert plate, turn over, and "give it a good downward shake", to remove from the ramekin.)