Line 2 baking trays with baking paper and set aside
Place flour, baking powder and salt into the Thermomix bowl and combine 10 sec/speed 10. Set aside.
Place sugar into the Thermomix bowl and mill 10 sec/speed 10.
Add butter and combine 20 sec/speed 6 or until fully combined. Scrape bowl down.
Insert butterfly 1 min/Butterfly/speed 3.
Add egg and vanilla and combine 10 sec/speed 3.
Remove butterfly and scrape down side of bowl.
Add the flour mix and combine 10 sec/speed 5.
Roll dough out on a floured silpat mat in a rectangle shape, wrap up and refrigerate for 1 hour
Preheat oven to 175°C.
Roll out cookie dough on to a floured bench and cut into 5cm x 5cm squares. The more accurate you are at this stage, the better they will look later. Place onto prepared trays. They won't spread, so they can be quite close together on the tray.
Bake for 11 minutes, or until the edges have started to brown. Leave on baking tray for 5 minutes, then transfer to a cooling rack.
Decorate when completely cold.
Make the royal icing and keep covered with a damp tea towel.
Dip each cookie into the icing and let it drip off until it starts setting, flip it over and lay back on the lined tray. Allow to set overnight or at least 8 hours before proceeding with the candy stripe.
To make the candy stripe colour, combine a little rose spirit, some rose or pink coloured lustre dust and a drop of the peppermint oil in small bowl. Stir together quite vigorously.
Arrange the iced cookies so they are touching. Dip a clean makeup brush the thickness of the candy stripe you want and paint across the cookies all at once. Add as many or as few stripes as you wish. When arranging the cookies later, switch them around so they have contrasting directions of stripes!