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

Cream together the softened butter and granulated sugar in a large bowl until light and fluffy. Use an electric mixer for best results.

Beat in the eggs one at a time, then stir in the vanilla extract.

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

Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Avoid overmixing.

Drop rounded tablespoons of dough onto the prepared baking sheets, leaving about 2 inches between each cookie.

Sprinkle with coarse sugar, if desired.

Bake for 10-12 minutes, or until the edges are set and the centers are still slightly soft. Let cool on baking sheets for a few minutes before transferring to a wire rack to cool completely.