1 Prepare the oven and pan: Preheat the oven to 350℉. Line a 9×13-inch ungreased glass baking dish with parchment paper, leaving enough of the paper hanging over the sides to use as a sling to remove the bars once they’re baked.
2 Make the crust: Add the graham crackers to the bowl of a food processor and pulverize them until they are finely ground and resemble sand. You should have a little over 3 cups once ground. (If you don’t have a food processor you can also do this by placing the graham crackers in a ziptop bag and smashing them with a rolling pin.)
Add the melted butter, light brown sugar, and salt; pulse until fully combined.
3 Transfer to the prepared baking dish: Spread the graham cracker mixture evenly in the prepared baking dish. Use your fingers and the bottom of a dry measuring cup to help press the mixture into the bottom and up the sides of the dish.
4 Bake the crust: Transfer the baking dish to the oven and place it on the center rack. Bake for 12 minutes, or until the crust darkens a bit and smells slightly caramelized. Remove from the oven and cool slightly.
5 Make the custard: In a large mixing bowl, whisk together the pumpkin puree, light brown sugar, cream, eggs, cinnamon, ginger, cloves, cardamom, nutmeg, salt, and vanilla, until smooth and well-combined. Pour the custard over the graham cracker crust.
6 Bake the bars: Transfer the pan to the oven and bake until the custard is set (the surface should look dry, taut, and the center should be firm), 50 to 60 minutes.
7 Remove from the oven and cool: Place the baking dish on a wire rack, and cool completely, at least 2 hours. Transfer to the refrigerator for at least 1 hour.
8 Make the whipped cream: While the bars chill in the refrigerator, make the whipped cream.
In a well-chilled bowl, whisk together the cream and vanilla until stiff peaks begin to form. (If doing this by hand, this could take 10 to 15 minutes or more.) If you want to learn all about properly whipped cream read our post: How to Make Whipped Cream.
Once the cream has been whipped to stiff peaks, fold in the finely chopped candied ginger. If you’re piping the whipped cream onto the bars, pay close attention to how finely chopped the ginger is so it doesn’t clog the piping tip.
9 Cut the bars: When the bars are chilled, lift the parchment ends and remove from the pan. Use a long sharp knife to cut the pie into bars. For the cleanest lines, cut straight down rather than dragging the knife through the bars, and carefully wipe the blade between each cut.
10 Serve: Spoon or pipe a dollop of whipped cream on top of each bar, garnish with a piece of candied ginger, and serve.