Preheat the oven to 180 °C. Line 2 large baking trays with silicone sheets or baking paper.: You should feel the kitchen warming as the oven approaches 180 °C , and the aroma from a warm oven feels reassuring. Proper tray preparation ensures even baking and easy release, so line two large trays with silicone sheets or baking paper to prevent sticking. If you crowd the tray, biscuits will spread into each other instead of keeping round shapes. One mistake is not rotating trays midway, which can cause uneven browning, so plan to swap positions halfway through baking.
Using an electric mixer, cream the butter.: As you beat the softened butter , you should see it transform from pale and dense to light and slightly fluffy, with tiny air bubbles forming. This aeration is crucial for a tender texture, because trapped air expands in the oven and lifts the dough. If you rush this step, the butter will remain heavy and the biscuits will be dense. Avoid overheating the butter with vigorous mixing at high speed for too long, which can make it greasy and reduce the biscuit lift.
Sift together the icing sugar, cornflour, and cake flour, then add this, along with the vanilla extract, to the creamed butter and beat until you have a light, fluffy dough.: When you sift the icing sugar , cornflour , and cake flour , you remove lumps and introduce air, producing a silkier dough. After adding the sifted dry ingredients and vanilla extract to the creamed butter , beat just until the mixture holds together as a pale, slightly billowy dough. You should notice a fine, delicate scent of vanilla and a smooth texture. Overmixing at this point develops gluten and can make the biscuits tougher, so stop as soon as the dough is cohesive. A common trap is adding extra liquid if the dough seems dry, which will change the texture and spreading behavior.
To create evenly sized biscuits, put the mixture into a piping bag and pipe out rounds onto the baking tray, leaving space in between for the biscuits to spread. Alternatively, simply drop teaspoonfuls of the mixture onto the tray. Decorate any way you like.: Piping produces uniform rounds with pretty ridges, while dropping teaspoonfuls gives a more rustic look. As the dough hits the tray, you should notice a slight sheen and a smooth surface ready for decoration. Leave adequate space between rounds so they can spread to their natural size, and press halved glacé cherries or sprinkles gently onto the tops so they adhere. A frequent error is piping too close together which causes the biscuits to fuse; space them well and keep the tray level when transferring to the oven.
Bake for 15–20 minutes, or until they just start browning on top. Leave to cool on a cooling rack.: During baking you will hear a quiet settling and see edges turn slightly paler gold while centers remain light, which signals readiness. Aim for the moment they just begin to brown on top; this ensures a tender center and a delicate, slightly crisp edge. Once out of the oven, transfer to a cooling rack so air circulates and they set without steaming underneath. Leaving them too long on a hot tray can lead to overbrowning, and underbaking will cause them to crumble. If you notice uneven browning, check oven temperature accuracy or rotate trays next time.