Preheat oven to 350 F. Line two baking sheets with parchment paper.
In a medium bowl, sift together the flour, malted milk powder, cocoa, baking powder and salt. Set aside.
In the bowl of a stand mixer, beat the butter and sugar together on medium speed until very smooth.
Add the eggs, one at a time. Beat in the vanilla. Don’t be concerned if the mixture looks curdled; it will even out once the dry ingredients are added.
Reduce the mixer speed to low, add half the dry ingredients, mixing until they just disappear into the batter.
Mix in the milk, then the remaining dry ingredients, mixing only until they are incorporated.
Fold in the malted milk balls and chocolate pieces.
Drop the cookie dough onto the prepared baking sheets, one rounded tablespoon per cookie, leaving about 2 inches between each.
Bake for 11 to 13 minutes. Let cool.