Take a 9x13 cookie sheet and line with parchment paper. A trick to get the parchment paper to lay flat is to scrunch up the piece in your hands and then flatten out.
Using a double boiler, gently melt the white chocolate.
Add the peanut butter and stir until combined.
Pour into the parchment paper, spreading to the corners with a spatula.
Melt the dark chocolate chips by microwaving 30 seconds at a time until melted. Stir until smooth.
Pour the dark chocolate in strips lengthwise.
Take a chopstick and swirl the dark chocolate into the white chocolate.
Set aside for an hour or so to set and cool, then place in the refrigerator for another couple hours.
Cut into pieces and enjoy! (Store wrapped in parchment paper in the freezer if desired.)
