Cut your white and dark chocolate into small pieces, then place them into two small bowls. (you can also use chocolate chips if you like)
In a small saucepan, heat the whipping cream (200ml) over medium heat just until it comes to a simmer. Pour the hot cream directly over the chopped white and dark chocolates into 2 equal amount and let stand for about 5 minutes to allow the hot cream to melt the chocolate. After about 5 minutes give both the chocolate a very good stir to completely melt the chocolate.
Once the chocolate is completely melted and smooth, set aside, let it cool for 5-10 minutes.
In a large bowl, whisk 300ml very cold whipping cream until soft peaks form. Then take half of the whipped cream in a separate bowl.
Add the cooled melted white chocolate to the whipped cream, in portions and continue to whisk until all the chocolate are mixed properly and firm peaks form. Repeat the same process with the rest of the whipped cream and cooled melted dark chocolate.
Spoon both the white and dark chocolate mousse in small serving dishes in layers, or put them into 2 piping bags and then pipe into the serving dish to make them look fancy. You can serve the mousse right away or refrigerate them for 3-4 hours before serving and it is better to serve chilled.
Decorate with some chocolate sprinkles or toppings of your choice and enjoy!