Preheat Oven & Line Tray: Preheat your oven to 320ºF (160ºC) fan-forced and line a baking sheet with parchment paper, set aside.
Prepare Mixing Equipment: Use a stand mixer with the paddle attachment, or a large mixing bowl with an electric hand beater.
Cream Butter, Sugar & Vanilla: Add softened butter, powdered sugar, and vanilla extract to the bowl. Beat on high speed for 1 minute, scraping down the sides as needed until smooth and creamy.
Incorporate Dry Ingredients: Sift in the flour and cornstarch. Mix on low-medium speed until a crumbly dough forms. Use your hands to gently bring the dough together, kneading lightly into a smooth ball.
Chill Dough: Wrap the dough in plastic wrap or cover the mixing bowl and refrigerate for 30 minutes to firm up.
Prepare for Rolling: Remove the dough from the fridge and let it sit at room temperature for 10 minutes to soften slightly.
Roll Out Dough: Lightly flour your work surface or a sheet of baking paper. Roll the dough out to a thickness of 3-4mm (1/8 inch). Dust with additional flour if it starts to stick.
Cut Out Shapes: Use festive cookie cutters to cut out shapes from the dough. Place the cookies onto the prepared baking tray. Gather and re-roll any scraps to use up all the dough. You may need multiple trays.
Chill Before Baking: Place the baking tray(s) with the cut-out cookies into the refrigerator for 15 minutes to firm up the dough again.
Bake Cookies: Bake for 12-14 minutes or until the edges are pale and just lightly golden. Avoid overbaking.
Cool Cookies: Remove the tray from the oven and let the cookies cool on the tray for 5 minutes. Then transfer them to a wire rack to cool completely. Decorate if desired, enjoy!