In a large mixing bowl, cream together 1 cup of softened unsalted butter with ½ cup of granulated sugar and ½ cup of powdered sugar until the mixture is light and fluffy, about 3-4 minutes. Add 1 teaspoon of pure vanilla extract and mix well.

In a separate bowl, whisk together 2 cups of all-purpose flour, ¾ cup of unsweetened cocoa powder, ½ teaspoon of salt, and 1 teaspoon of baking powder until evenly mixed. Gradually incorporate this mixture into the wet ingredients until just combined.

If desired, fold in ½ cup of chopped nuts. Cover the bowl with plastic wrap and chill the dough in the refrigerator for at least 30 minutes.

Preheat your oven to 350°F (175°C). Scoop portions of the chilled dough (about 1 tablespoon each) and form them into balls, making an indentation in the center to place a chocolate chunk, then encase the chocolate and roll the dough into a ball.

Line a baking sheet with parchment paper and arrange the cookie balls, leaving space between them. Bake for 10-12 minutes or until the edges are firm but the centers remain soft.

Remove the cookies from the oven and let them cool for about 5 minutes before transferring to a wire rack. Roll in powdered sugar when cool.