Preheat oven to 350°F (175°C) and line baking sheets with parchment paper.

In a large bowl, cream together the butter, 1/2 cup granulated sugar, and brown sugar until light and fluffy.

Beat in the egg and vanilla extract until fully incorporated.

In a separate bowl, whisk together the flour, cocoa powder, baking soda, and salt.

Gradually add the dry ingredients to the butter mixture, mixing until just combined.

Shape the dough into 1-inch balls and roll each ball in the extra granulated sugar.

Place dough balls 2 inches apart on the prepared baking sheets.

Bake for 8 to 10 minutes until the edges are set.

Remove from the oven and immediately press one chocolate candy drop into the center of each cookie.

Allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.