01 - Whisk together flour, baking soda, baking powder, salt, cinnamon, ginger, and nutmeg in a medium bowl.
02 - Using an electric mixer in a large bowl, beat softened butter, granulated sugar, and brown sugar until light and fluffy.
03 - Add egg, pumpkin purée, and vanilla; blend until smooth.
04 - Gradually mix in the dry ingredients until the dough is just combined.
05 - Cover mixture and refrigerate for at least 1 hour for easier shaping.
06 - Preheat oven to 350°F. Dust the work surface lightly with flour, then roll dough to 1/4-inch thickness. Cut into 2-inch round or pumpkin shapes using cookie cutters.
07 - Transfer cookies to parchment-lined baking sheets. Use a small paring knife to carve faces into half the cookies.
08 - Bake at 350°F for 10–12 minutes, just until set but still soft. Cool completely on a wire rack.
09 - Place a scoop of vanilla ice cream on the bottom of a plain cookie. Cap with a Jack-o'-Lantern face cookie, pressing gently to adhere.
10 - Arrange sandwiches on a tray and freeze for at least 30 minutes.
11 - Before serving, accentuate faces with black decorating gel or melted chocolate if desired.