In a large bowl, mix together the melted butter, cocoa powder, and sugar.
Whisk in the eggs and vanilla.
In a separate bowl, stir together the flour, baking soda, and salt.
Slowly add the dry ingredients to the chocolate mixture. Next, stir in the chocolate chips.
Cover and refrigerate the dough for 1 to 2 hours.
Preheat the oven to 350°F.
Prepare the baking sheets using parchment paper or a silicone baking mat.
Form the dough into 1 inch balls, then roll the balls in the powdered sugar.
Bake for 10 minutes.
Allow the cookies to rest for 2 to 3 minutes before removing them from the baking sheet to a cooling rack. Allow the baking sheet to return to room temperature before adding more cookie dough (see notes).
Store in an airtight container for up to 5 days.