Beat the softened butter, powdered sugar, and vanilla together until light and fluffy, about 2 minutes.
In a separate bowl, whisk together the flour, cocoa powder, and salt until no cocoa streaks remain.
Add the dry ingredients to the butter mixture and mix on low just until a soft dough forms.
Fold in the mini chocolate chips by hand with a spatula.
Scoop and roll the dough into 1-inch balls and place them 2 inches apart on a parchment-lined baking sheet.
Bake at 350F for 9 to 11 minutes, until set around the edges but still soft in the center.
Let the cookies rest on the baking sheet for 2 to 3 minutes.
Roll each cookie in powdered sugar while still warm, then let cool completely and roll a second time.
