Put 1/2 cup of the milk in a 6- or 8-cup saucepan, and sprinkle the gelatin over it. Let sit for 5 minutes. Meanwhile, blend together the remaining milk, cream, pumpkin, sugar and cinnamon. The mixture should be perfectly smooth, so it is best to use a blender.
Turn the heat under the saucepan to low, and cook the milk, stirring occasionally, until the gelatin dissolves. Pour in the cream mixture, and turn the heat to medium. Cook, stirring occasionally, until steam rises. Turn off the heat, and ladle or pour the mixture into 6 4-ounce ramekins or other containers.
Chill the panna cotta until firm, and serve, with creme fraiche or whipped cream if you like.