In a large bowl, whisk together the pumpkin, eggs, evaporated milk, brown sugar, cornstarch, pumpkin pie spice, salt, and vanilla until completely smooth.
Set 6 ramekins on a rimmed baking sheet and divide the custard evenly among them.
Bake and Chill
Bake at 350°F until the edges are set and the centers still have a slight jiggle, about 30 to 40 minutes. Do not overbake.
Let the custards cool to room temperature, then chill at least 2 hours until firm. Top with whipped cream and a dusting of cinnamon to serve.
Notes
Pull them while they jiggle: A slight wobble in the center sets up perfectly as it cools; overbaking causes cracks.
Water bath: Setting the ramekins in a pan of hot water gives the silkiest set.
Storage: Keeps covered in the fridge up to 4 days, or freeze up to 2 months and thaw overnight.