Prepare an 8x8 square baking pan by lining with foil. Coat foil with non-stick cooking spray. Set aside.

In a small bowl, place white chocolate chips and peanut butter. Heat for about 1 ½ minutes in the microwave, stopping at 30 second intervals to stir until the mixture is smooth and chips are fully incorporated.

Pour peanut butter mixture into prepared pan and spread in an even layer. Set aside.

Repeat melting process with semi sweet chips {it will take less time since it's a smaller amount}.

Spoon melted chocolate over peanut butter mixture in long tiger-stripe-like strokes.

With the tip of a knife or a toothpick, swirl chocolate into peanut butter mixture to look like tiger stripes.

Chill in freezer for about 15 minutes or until set, then remove and break into pieces.