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

In a mixing bowl, cream together the softened butter and granulated sugar until light and fluffy, about 3-5 minutes.

In another bowl, combine the flour, cocoa powder, and salt. Gradually add this dry mixture to the butter mixture, mixing well after each addition.

Stir in the vanilla extract until well incorporated.

Using a tablespoon or small cookie scoop, form the dough into small round balls (about 1 inch in diameter). If using nuts, you can incorporate them into the dough or add them to the exterior while forming the balls.

Place the cookie balls on the prepared baking sheet, spacing them about 2 inches apart.

Bake in the preheated oven for 10-12 minutes until they're firm but still soft in the center.

Allow the cookies to cool on a wire rack for about 5 minutes.

While still warm, roll them in powdered sugar until completely coated.

Let the cookies cool completely and roll them one more time in powdered sugar before serving or storing.