Add the butter and white sugar to a medium sized bowl and beat until light and fluffy.
Add the egg and the vanilla and mix through.
In a small bowl, mix the plain flour, baking powder and salt together.
Slowly mix the dry mixture into the butter mixture until well combined.
Weigh the dough and divide it into thirds.
Roll 2 of the thirds together and wrap in cling wrap.
Add the remaining third to a bowl and mix in the brown sugar, cinnamon and nutmeg.
Wrap this dough in cling wrap.
Place both of the doughs into the fridge and chill for around an hour.
Remove the first lot of dough from the fridge and roll it out into a thin layer, rectangular in shape, between sheets of baking paper.
Place in the fridge and repeat with the second lot of dough. Let the rolled out dough chill in the fridge for about 15 minutes.
Remove the doughs from the fridge and carefully peel back the baking paper on the plain dough.
Remove the baking paper from the spiced dough and lay it on top of the plain dough, trying to get the edges as even as possible.
Once they are together, starting at the long end, roll up the dough into a log.
Wrap the log in cling wrap and chill in the fridge for at least 1 hour as this helps the dough to hold its shape when being cut.
Preheat the oven to 177˚C (350˚F). Line a baking tray with baking paper.
Remove the dough log from the fridge and cut into ¼ " thick slices with a sharp knife.
Place the cookie slices on prepared baking tray about 2" apart.
Bake for 8 to 10 minutes, until the edges turn a light golden colour.
Remove from the oven and place on a cooling rack.
Making the Glaze
Combine the icing sugar, vanilla and milk in a small bowl.
Whisk until the mixture has a runny consistency. If you find it is too dry, try adding a small amount of milk until you get the desired consistency.
Drizzle the glaze over the cookies. This can be done while still warm, which may result in the glaze melting into the cookies. Or, you can glaze the cookies when they have completely cooled down.
Nutritional information is an estimate and provided as a courtesy. The values may vary according to the ingredients and tools that are used. Please use your preferred nutritional calculator for more detailed information.