Step 1

Make the graham cracker crust: Preheat the oven to 400°F with a rack in the center position. Grease a sheet pan with nonstick spray.

Step 2

In a food processor, grind together the graham cracker crumbs and nuts until coarsely ground and well combined. Add the brown sugar, granulated sugar, melted butter, and salt and pulse to com- bine until the mixture resembles wet sand.

Step 3

Pour the graham mixture evenly into the prepared pan and use your hands or a flat-bottomed measuring cup to press the crumbs firmly against the bottom and up the sides of the pan, making sure there are no holes or extra-thin spots anywhere.

Step 4

Make the pumpkin filling: In a large bowl, whisk together the pumpkin puree, granulated sugar, salt, cinnamon, ginger, cloves, and nutmeg until smooth. Whisk in the eggs until smooth, then add the milk and cream and whisk until homogeneous.

Step 5

Pour the pumpkin custard over the prepared crust and very carefully transfer the pan to the oven. Bake the bars for
 15 minutes, then reduce the oven temperature to 350°F and bake for 10 to 15 minutes more, until the custard is mostly set— the center should just barely jiggle. Allow the pumpkin bars to cool in the pan for 20 minutes before transferring to the refrigerator, uncovered, to cool completely, at least 30 minutes and up to overnight.

Step 6

Meanwhile, make the whipped cream, if desired: In the bowl of a stand mixer fitted with the whisk attachment or in a large bowl with a handheld mixer, whip the cream and granulated sugar on medium-high speed until soft peaks form, about 3 minutes.

Step 7

Slice the pumpkin bars into squares or triangles and serve topped with a generous dollop of whipped cream. The bars will keep, tightly covered, in the refrigerator for up to a week.