Leave the butter at room temperature before starting to bake. Use the paddle attachment to mix the butter, powdered sugar, and cornstarch until smooth and silky.
1 cup Butter, ¾ cup Powdered sugar, ¼ cup Cornstarch
Add the egg yolk and vanilla extract.
1 Yolk, 1 teaspoon Vanilla extract
Mix the flour, cinnamon, and salt. Add the mixture in two or three passes, mixing well after each. You will end up with a soft and smooth dough.
2½ cup All-purpose Flour, ½ teaspoon Salt, 1 teaspoon Cinnamon
Shape the dough into a disc, cling wrap, and chill for one hour.
Lightly flour a clean surface and roll out the dough. For easier rolling, place the dough between two pieces of wax paper. Once the dough is ¼ of an inch thick, use your cookie cutter to cut it.
This dough makes about 20 sandwich cookies or 40 individual cookies. Stamp 20 cookies with the pumpkin stamp and cut out the eyes and mouth. Leave the other 20 cookies plain.
Place the raw cookies on a lined baking sheet in the fridge for 5-10 minutes. In the meantime, preheat the oven to 325F. Bake the cookies for 8-10 minutes or until the edges look set. Do not overbake them, as this will make them dry and brown. Let them cool down for a few minutes, then transfer them to the cooling rack to cool down fully.
Place about one tablespoon of Nutella on the plain cookie, place the stamped cookie on top, and gently press.
¾ cup Nutella