Place white chocolate in a 1 1/2 quart microwave-safe bowl. Microwave on high 2 minutes or until melted. Add peanut butter and microwave on high 2 minutes or until mixture is smooth and creamy. Blend well. Spread mixture into a 15 1/2 x 10 1/2 inch jellyroll pan lined with waxed paper.
In a 2 cup microwave-safe meausuring cup, melt chocolate morsels onHigh approximately 2 inutes. Pour melted chocolate over peanut butter mixture, swirl with a knife to create a marble effect or drizzle melted chocolate on top of mixture using a fine tip of a pastry tube. Chill unti set and cut into squares.