1. Preheat your oven to 300°F or 150°C. Line a baking sheet with parchment paper to ensure the meringue doesn't stick.

2. In a large mixing bowl, whip the egg whites until they form stiff peaks. This should take a few minutes with an electric mixer. Gradually add 200g or 1 cup of granulated sugar and continue whipping until the mixture is smooth and glossy.

3. Next, fold in 120g or 4 cups of Rice Krispies cereal gently until it's well combined with the egg mixture. Be careful not to crush the cereal.

4. Spoon the mixture onto the prepared baking sheet and spread it evenly to form a flat layer.

5. Bake the meringue in the preheated oven for 1 1/2 hours or until it's dry and crisp. Allow it to cool completely on the baking sheet.

6. In a separate bowl, whip 240ml or 1 cup of heavy whipped cream until it forms stiff peaks. This will add a rich and creamy texture to your dessert.

7. Arrange sliced strawberries, blueberries, and shaved white chocolate on top of the cooled meringue. You can use as many or as few as you like, depending on your preference.

8. Finally, top the meringue with the whipped cream and serve immediately. This dessert is best enjoyed fresh.