Add the white chocolate chips in a microwave-safe bowl and cook on high for about 30 seconds at a time, stirring in between, until it is melted. It took about 90 seconds for me. However, microwaves vary in strength and cook times, and yours could vary.
Cover a cookie sheet with wax paper. Pour the melted white chocolate evenly onto the wax paper. Spread with a spatula to even it out.
Place blueberries and raspberries evenly throughout the melted white chocolate. Do this right away before the white chocolate hardens.