Preheat your oven to 170°C (335°F), non-fan / conventional oven setting and line your baking sheet with your silicone baking mat. This step ensures your cookies won't stick to the sheet while baking.
Place the softened butter and flavouring into the bowl of your stand mixer and mix these together until they are combined, this should only take a few seconds. By adding the flavouring to the butter, this helps to enhance the flavour.
Add the castor sugar to the mixture and mix this in until they are all combined and the mixture becomes light and fluffy. Mixing the butter and sugar is crucial for achieving that perfect cookie texture, but you need to be careful not to over mix as this can cause the cookies to spread.
Add the egg to butter-sugar mixture and mix this in until all are well combined. This step adds moisture to the dough.
In a separate bowl, sift the all-purpose flour, corn flour, and salt and give these a whisk to make sure they are properly combined. Properly combining the dry ingredients makes sure everything is evenly distributed which helps to enhance the cookie's texture.
Gradually add the dry ingredients to the wet ingredients in your stand mixer, mixing well after each addition. The dough should start to come together and have a slightly firm texture without being too sticky. Avoid overmixing, as it can toughen the cookies and cause them to spread too.
Split your dough into two balls, leave one in the bowl and place the other on a piece of parchment and press this down with your hands to about 1 inch thick. Next place another piece of parchment on top of your dough and roll the dough to about 6mm (1/4 inch) thick. You can achieve an even thickness by using a rolling pin that has guides or you can use dowls either side of your dough and roll over these. Achieving an even thickness of your cookies will help these to bake evenly.
Select your favourite cookie cutters and use these to cut out your shapes from the rolled-out dough. Transfer the cookies to your prepared baking sheet, leaving a little space between each cookie just to allow for minimal spreading. When transferring your cookies, you can use a cookie spatula to pick these up to help to prevent the shapes becoming distorted.
Place the baking sheet with your cookies on it in the preheated oven for 12-14 minutes or until the edges are lightly golden. The exact baking time will depend on the thickness of your cookies and your oven, so keep an eye on them to avoid over-baking.
Once the cookies are done, remove them from the oven and let them cool on the baking sheet for a 5-10 minutes before transferring them to a wire rack to cool completely. Once your cookies are fully cooled, you can decorate the cookies with your favourite icing, sprinkles or even just enjoy as they are.