Leave the butter at room temperature before starting to bake. Mix the butter, powdered sugar, cornstarch, and salt until smooth and silky.
1 cup Butter, ¾ cup Powdered sugar, 1 tablespoon Cornstarch
Add the egg yolk and vanilla extract.
1 Egg yolk, 1 teaspoon Vanilla extract
Add the flour in two or three passes and mix well after each. You would have a soft and smooth dough in the end.
2¼ cups Flour, ¼ teaspoon Salt
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 favourite cookie cutter to cut the dough.
Place the raw cookies on a lined baking sheet and in the fridge for 15 to 20 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 it makes them dry and brown. Let them cool down for a few minutes, then transfer them to the cooling rack to cool down fully.
If you are dusting or icing them, dust or ice them first, then assemble them with the filling.