In a large bowl, cream together butter and sugar.
Mix in eggs one at a time and then vanilla.
In another bowl whisk together flour, cocoa powder, baking powder and salt.
Gradually stir dry ingredients to wet, until incorporated.
Cover with plastic wrap and refrigerate for at least 1 hour.
Preheat oven to 350.
Line a baking sheet with parchment paper.
Place powdered sugar in a shallow dish.
Roll dough into 1" sized balls.
Roll balls in powdered sugar and place on prepared sheet, flattening slightly.
Bake for 9-10 minutes (do not overbake).
Gently press a chocolate kiss into the center of each hot cookie.
Allow cookies to cool on baking sheet before removing.