Preheat oven to 350F. Line 2 baking sheets with parchment paper and set aside.
Place butter and sugar in the bowl of a large stand mixer, fitted with a paddle attachment OR in a large mixing bowl with a wooden spoon. Mix on medium speed or by hand until creamy, about 2 minutes. Add egg and vanilla, beating well until smooth.
In a medium separate bowl, combine flour, cocoa, baking soda, and salt. Add to butter mixture, beating on medium speed until dough is just combined.
Scoop dough into 1-inch balls and roll in turbinado sugar. Place balls 2 inches apart on prepared baking sheets and flatten slightly.
Bake cookies at 350F 10-12 minutes until cookies are crackly (middles will be slightly soft). Allow cookies to cool on baking sheet 20 minutes before transferring to a wire cooling rack to cool completely. Enjoy!
Notes
Storing InstructionsStore cookies in an airtight container at room temperature up to 4 days.