Place butter, sugar and vanilla in a large mixing bowl and beat with a stand or electric mixer until combined. Add the eggs, one at a time, and mix on medium-low speed just until combined - about 10 seconds each.
Add cocoa powder, flour, baking powder and salt in a medium bowl and mix on low speed until incorporated.
Cover the bowl and chill the dough for at least 1 hour or up to overnight (the longer you chill, the thicker the cookies will be).
When ready to bake, preheat the oven to 350°F. Place the powdered sugar in a medium bowl. Roll the dough into tablespoon-sized balls and cover them well with the sugar.
Place on a lined baking sheet with enough space between them and bake for 10-15 minutes, or until spread and crackled. The cookies will look soft in the center but will firm up as they cool. Don't over bake.
Notes
For perfect crinkles, don’t skip chilling the dough.
Be generous with the powdered sugar coating for a striking contrast.
Store cookies in an airtight container for up to 5 days.