Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

In a large mixing bowl, cream together softened unsalted butter, granulated sugar, and brown sugar until light and fluffy.

Add in one large egg and vanilla extract, mixing until fully combined.

In a separate bowl, whisk together all-purpose flour, baking soda, and salt, then gradually incorporate into the wet ingredients.

Divide the cookie dough into two equal portions. Stir creamy peanut butter into one half and melted chocolate chips into the other half.

Drop spoonfuls of each flavored dough onto the prepared baking sheet, about 2 inches apart, and gently swirl them together.

Bake the cookies for 10 to 12 minutes until the edges are golden and the centers are soft.

Cool the cookies briefly on the sheet before transferring them to a wire rack.