Preheat your oven to 350°F (175°C). Line an 8x8-inch baking pan with parchment paper.

In a medium bowl, combine graham cracker crumbs, granulated sugar, and ground cinnamon. Pour in the melted butter and mix until it resembles damp sand. Press this mixture into the bottom of the prepared pan.

Bake the crust in the oven for 8-10 minutes, until golden and fragrant. Allow it to cool slightly.

In a large bowl, whisk together the mashed sweet potato, brown sugar, eggs, evaporated milk, and vanilla extract. Mix in ground cinnamon, nutmeg, ginger, and salt until smooth.

Pour the filling over the cooled crust and evenly spread it. Bake for 35-40 minutes until set.

Let the bars cool completely in the pan on a wire rack. Cover and refrigerate for at least 1 hour.

Lift the bars out using the parchment paper and slice into portions. Serve with whipped cream if desired.