Preparation Steps

• In a large bowl, cream together the softened butter and granulated sugar until light and fluffy.
• Beat in the egg and vanilla extract until well combined.
• In a separate medium bowl, whisk together the flour, baking soda, and salt.
• Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Divide the dough in half.
• In a small bowl, mix one half of the dough with the cocoa powder until evenly combined.
• On a lightly floured surface, roll out each half of the dough into a rectangle of approximately the same size (about 10x12 inches).
• Carefully stack the chocolate dough rectangle on top of the vanilla dough rectangle. Gently press them together.
• Starting from one of the longer sides, tightly roll up the stacked dough into a log.
• Wrap the log tightly in plastic wrap and refrigerate for at least 1 hour, or until firm.
• Preheat your oven to 350°F (175°C). Line baking sheets with parchment paper.
• Unwrap the chilled dough log and slice it into 0.25-inch thick cookies.
• Place the cookies on the prepared baking sheets, leaving about 2 inches between them.
• Bake for 10-12 minutes, or until the edges are lightly golden brown.
• Let the cookies cool on the baking sheets for a few minutes before transferring them to a wire rack to cool completely.