1️⃣ Make the dough base: In a large bowl, cream butter and sugar until fluffy. Mix in egg and vanilla. In a separate bowl, whisk together flour, baking powder, and salt. Gradually add to the wet mixture until a soft dough forms.

2️⃣ Divide and flavor: Divide the dough in half. To one half, knead in peanut butter and powdered sugar. To the other half, knead in cocoa powder and a bit of milk until smooth.

3️⃣ Roll out layers: Roll each dough half between parchment paper into matching rectangles about ¼ inch thick.

4️⃣ Assemble the swirl: Carefully stack the chocolate layer on top of the peanut butter layer. Gently press together and trim edges for clean sides. Roll tightly into a log, using the parchment to help guide.

5️⃣ Chill the dough: Wrap in plastic wrap and refrigerate for at least 1 hour, or until firm.

6️⃣ Slice and bake: Preheat oven to 350°F (175°C). Slice chilled dough into ¼-inch rounds and place on a parchment-lined baking sheet. Bake for 9–11 minutes until set.

7️⃣ Cool and serve: Let cool on the sheet for a few minutes, then transfer to a wire rack. Enjoy!