Mix the chocolate base: In the bowl of a stand mixer (or using a hand mixer), combine 1 cup unsweetened cocoa powder, 1 ¼ cups granulated sugar, and ½ cup plus 1 tablespoon melted butter. Beat together on medium speed until the mixture looks shiny but still feels slightly gritty from the sugar.
Add eggs and vanilla: Beat in 4 large eggs, one at a time, making sure each egg is fully incorporated before adding the next. Then add 1 tablespoon vanilla extract and beat for an additional minute until smooth.
Combine dry ingredients: In a separate bowl, whisk together 2 cups all-purpose flour, 2 teaspoons baking powder, and ½ teaspoon salt. Gradually add the dry ingredients to the chocolate mixture, mixing just until combined—don’t overmix.
Chill the dough: Cover the bowl with plastic wrap and refrigerate the dough for at least 4 hours (or overnight). Chilling helps the dough firm up and ensures the cookies develop their signature crinkled tops.
Preheat and prepare: When ready to bake, preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper or silicone baking mats.
Shape and coat: Place 1 cup powdered sugar in a shallow bowl. Using a small cookie scoop (about 1 ½ tablespoons), portion out dough balls and roll each one in the powdered sugar until completely coated. Don’t worry if there’s a little extra sugar—it adds to the charm!
Bake: Arrange the coated dough balls on the prepared baking sheets, leaving about 2 inches between each. Bake for 12–15 minutes, or until the tops are cracked and set but the centers are still slightly soft.
Cool and enjoy: Let cookies cool on the baking sheet for 2–3 minutes before transferring them to a wire rack. Allow to cool completely before serving.