Combine the butter, cream cheese, pumpkin, sweetened condensed milk, and pumpkin pie spice in a skillet over medium heat. Stir constantly until thickened and well-combined. Stir in the graham crackers and white chocolate chips until melted and smooth. Add a few drops of food coloring if desired.

Continue to stir until the pumpkin cheesecake mixture releases from the sides and bottoms of the pan when stirred. (If in doubt, cook a bit longer—it's better to be thicker than too thin.)

Pour over a butter-greased baking sheet. Spread into an even layer and refrigerate until firm, about 2 hours, or overnight.

Rub butter on your hands to prevent sticking and then roll the chilled pumpkin cheesecake dough into small balls.

Pour granulated sugar into a shallow bowl and roll the truffle balls in granulated sugar to coat.

Using a toothpick, make ridges along the sides of the pumpkin truffles. Top with chocolate chips to look like stems. Serve immediately or refrigerate until ready to serve.