Preheat the oven 350°F. Line 2 baking sheets with parchment paper.
Beat butter with confectioners sugar until light and fluffy.
Add the milk powder and vanilla extract; stir until combined.
Stir in the all purpose flour and baking powder and mix until combined. If the dough seems too dry, add a 1~2tbsp milk. If the dough is too wet, add 1~2tbsp of flour. The dough should be nice and pliable.
Lightly flour the work surface, roll out the dough into an ½" thick rectangle. Use a 2½~3" round cutter and cut the dough into crescent shape cookies. Re-roll the scraps and cut into more cookies.
Transfer the cookies onto the prepared baking sheets and bake for 8~10 minutes or until the tops are slightly firm and bottoms are lightly golden.
Remove from the oven and place them on cooking racks to cool completely.