Prepare the baking sheet: Use a 5cm/2inch round cookie cutter as a guide to draw circles on a sheet of parchment/ baking paper. This will serve as a guide to pipe even sized cookies. Space the circles about 1 inch/3cm apart. Turn the parchment paper over so that the pencil marks are underneath.
Beat the butter and sugar: In a large bowl, beat the butter and powdered sugar for about 5 minutes until pale and fluffy. See note 4
Add dry ingredients and extract: Sift the flour and corn flour into the butter mixture and beat for 2 minutes on medium speed until thoroughly combined. Add vanilla extract and beat for 20 seconds more to combine.
Pipe: Spoon the mixture into a piping bag fitted with an open star nozzle (1M).Pipe 24 swirls using the circles as a guide. (See video for below to watch how these cookies are piped.)
If you feel that the dough is too stiff or hard to pipe, then just add a tablespoon of warm milk to the dough. This will make the dough softer and easier for you to pipe
Refrigerate piped shapes: Place the baking sheet into the refrigerator for 30 to 40 minutes to firm up the piped cookies. See note 5
Bake: Preheat the oven to 350°F/180°C (160°C fan) Bake for 10 to 12 minutes until golden brown. Remove from the oven and leave the cookies on the baking sheet to cool for 10 minutes.
Cool: These cookies are very delicate so avoid using your hands to pick them off the baking tray. Rather use a spatula to transfer them to a cooling rack.
Once cooled serve as is or sandwich with buttercream and jam if you prefer. Keep in mind that these cookies are very delicate even after cooling so handle gently.