Arrange six 6 oz ramekins in a large, shallow baking pan. Put a large kettle of water on the stove and bring to a boil.
In a 2-quart saucepan, combine the cream, milk, and cinnamon stick and then scrape the seeds from the vanilla bean into the mixture. Warm the cream mixture over medium heat until small bubbles form around the edges, or 170°F. Remove from heat, cover, and steep for 10 minutes. Discard the vanilla bean and cinnamon stick.
While the cream mixture steeps, combine pumpkin puree, maple syrup, cardamom, nutmeg, and salt in a large heavy-bottomed saucepan. Bring to sputtering simmer over medium heat while stirring constantly until thick and shiny, about 10 minutes.
In a large bowl, whisk the eggs until pale, about 1 minute. Temper the eggs by slowly adding the warm pumpkin-cream mixture, whisking constantly. Strain the custard through a sieve into a large measuring cup.
Divide the egg mixture among the ramekins. Skim away any foam. Fill the baking pan with hot water until it reaches halfway up the sides of the ramekins. Cover tightly with tinfoil and bake until just barely set and the center still wobbles, about 45 to 60 minutes.
Remove the ramekins from the water bath and transfer to a wire rack to cool. Cover with plastic wrap and refrigerate until firm.
Just before serving, make the whipped cream. In a cold metal bowl, whip the heavy creme until soft peaks form. Top each pot de crème with a spoonful of cream and a sprinkle of crumbled gingersnap cookies.
Line a half sheet pan with a silicone baking mat.
In a 2-quart heavy saucepan, bring sugar, water, and salt to a boil over medium heat, stirring to dissolve the sugar.
Cook without stirring until mixture turns amber in color, about 20 minutes. If sugar crystals form, wash them down from side of pan with a pastry brush dipped in cold water.
Remove caramel from heat and stir in pumpkin seeds. Pour mixture onto the prepared sheet pan and carefully cover with a sheet of parchment paper. Immediately roll out brittle as thinly as possible with a rolling pin before removing parchment.
Cool completely, about 25 minutes, and then break into pieces. Store in an airtight container for up to 2 weeks.