Preheat your oven to 400 degrees Fahrenheit
Line your baking sheet with parchment paper and set aside until ready to use
In the bowl of your stand mixer, beat the butter until creamy. Slowly add in the sugar and powdered sugar and beat for a few minutes until mixture is light and fluffy.
Separate the egg, reserve the white and add the yolk to the butter mixture. Beat the mixture for another minute.
Add the flour, salt, baking powder and ground ginger and mix until just combined. Add the minced ginger and mix until just incorporated.
Cover the dough with a piece of cling film and pat into a rectangle. Place in the fridge to chill for ten minutes or so.
Roll out the dough on a lightly floured surface, or between two sheets of parchment paper to a thickness of ¼"
Use the round cookie cutter to cut out rounds from the dough. Re roll trimmings as needed until no dough is left.
Place biscuits slightly apart on lined baking sheet and bake for ten minutes or until cookies are firm and a pale golden color.
Remove cookies from the oven and brush with the egg white and sprinkle the turbinado sugar on top.
Place the biscuits back in the oven and cook for another 3 to 5 minutes or until the biscuits are a golden brown color.
Let the biscuits cool on the pan for a minute and then transfer to a wire rack to cool completely. Store biscuits in an airtight container at room temperature