1. Pre-heat oven to 160°C and set to convection (fan) setting.
2. Sift Prima Top and Superfine Wholegrain Flour, corn starch and salt together. Set aside.
3. Cream butter and icing sugar until light and fluffy.
4. Add in egg and mix until well combined.
5. Gradually add in the flour mixture and mix until a dough ball is formed.
6. Divide the dough into 2 portions and add your desired colouring and flavouring into one of the portions. Slightly flatten the dough into a rectangular shape and cover it in cling wrap. Let it chill in the fridge for 15-20 minutes.
7. Use a rolling pin to roll out the dough into 0.3-0.5 cm thickness and let the dough chill again for 5-10 minutes.
8. Stack both the plain and coloured dough on top of each other. Gently roll the dough up lengthwise to form a cylinder shape. Cling wrap the dough and let it rest in the freezer for 1 hour.
9. Slice the dough into 0.5-0.7cm thickness. Bake at 160°C for 15-20 minutes. Cool and serve.