Line a 9×9 glass pan with parchment paper or foil.
Put semi sweet chocolate chips in a small glass bowl. Microwave for 1 minute and stir until smooth. Set aside.
Pour vanilla chips in a separate medium sized glass bowl. Microwave for 1 minute. Stir gently until smooth. Add peanut butter and stir until well combined and smooth.
Pour vanilla-peanut butter mixture into the prepared pan. Once it’s settled, take the melted semi sweet chocolate and pour it onto the vanilla-peanut butter mixture in lines.
Take a knife and run it the opposite direction of the chocolate lines you created, to achieve a swirl pattern. Run your knife through the mixture as much as you’d like, to create your desired swirl pattern.
Let cool either on the countertop or in the refrigerator. Pull the foil or parchment paper to remove from the pan,
Cut into small squares. Store in an airtight container.