Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
In a large bowl, whisk together 2 cups of all-purpose flour, 1/4 cup sugar, 1 tablespoon baking powder, 1 teaspoon pumpkin pie spice, and 1/2 teaspoon salt.
Add the cold, cubed butter to the dry ingredients. Using a pastry cutter or two forks, cut the butter into the flour mixture until it resembles coarse crumbs with pea-sized bits of butter.
In a separate bowl, mix 1/2 cup pumpkin puree with 1/2 cup heavy cream and 1 teaspoon vanilla extract. Pour this wet mixture into the dry ingredients and gently stir until just combined. Be careful not to overmix — a few streaks of flour are okay.
Gently fold in 1/4 cup white chocolate chips and 1/4 cup chopped walnuts if using.
Turn the dough out onto a lightly floured surface and gently pat it into a circle about 1 inch thick. Using a sharp knife or a pizza cutter, slice the dough into 8 wedges.
Place the wedges on the prepared baking sheet, spacing them slightly apart. Bake for 18-22 minutes, or until the scones are golden brown and a toothpick inserted in the center comes out clean.
Allow the scones to cool on a rack for at least 15 minutes. Once cooled, use your decorative icing to pipe cute ghost faces on each scone. Let the icing set before serving.
