Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper or lightly grease it to prevent sticking.
In a large mixing bowl, combine creamy peanut butter, granulated sugar, unsweetened cocoa powder, and an egg.
Stir well until the mixture forms a smooth, thick dough. Make sure all ingredients are evenly combined.
Scoop out small portions of the dough (about 1 tablespoon each) and roll them into balls.
Place them on the prepared baking sheet, leaving about 2 inches of space between each cookie.
Use the back of a fork to gently press down on each dough ball, creating a criss-cross pattern on the top.
Bake the cookies in the preheated oven for 10-12 minutes, or until the edges are firm. The centers may still look slightly soft, but they will firm up as the cookies cool.
Remove the baking sheet from the oven and allow the cookies to cool on the tray for about 5 minutes. Then, transfer them to a wire rack to cool completely.