Combine flour, baking powder and salt in a medium bowl.
In a larger bowl, beat sugar and butter until pale in color, using an electric hand mixer or a stand mixer.
On a low speed, add your egg and milk until combined.
Then slowly add in your dry ingredients.
Cut in half and flatten into two disks.
Wrap in plastic wrap or parchment and chill for at least 2 hours.
Mix can be made ahead and stored in the freezer for up to three weeks.
Let cookie dough thaw if you have frozen it before proceeding.
Preheat oven to 375°.
On a clean surface, sprinkle your powdered sugar and roll out each disk to ¼ inch in thickness.
Use cookie cutters to form shapes.
Line sheet pan with parchment paper.
Place cut dough on parchment paper at least 1" apart.
Cook for 7-10 mins, or until the edges become a light brown.
Let stand for 3 mins and place onto a wire rack until completely cool.
Ice with Royal Icing.