Put the pieces of white chocolate in a bowl and microwave till the chocolate is melted. Keep aside.

Place the egg white in another bowl and whisk the egg white till it reached soft peaks. In a third bowl, whisk cream till soft peak and add vanilla extract.

Fold in the whipping cream to the chocolate followed by the egg white.

Once well incorporated, set aside.

Separate whites and yolk. Place whites in a large bowl and yolks in a small bowl.

Break chocolate into pieces and place in a microwave-proof bowl with the butter. Melt in the microwave in 30 second bursts, stirring in between, until smooth. Set aside to cool.

In another bowl, beat cream until stiff peaks form, being careful not to over-whip.

Whip whites for 1 minute. Add sugar and continue to beat whites until firm peaks form.

Beat yolks and vanilla till light and pale.

Fold egg yolks into cream using a rubber spatula. Some streaks is fine.

Pour chocolate into cream yolk mixture. Fold through.

Add 1/4 of beaten egg whites into chocolate mixture. Fold through until incorporated.

Pour chocolate mixture into egg whites. Fold through until incorporated and no more white lumps remain.

Repeat the same step for the dark chocolate mousse.

Transfer each mousse to a piping bag.

Place 1 tbsp of the Oreo in your serving dish and give it a good press. Refrigerate for 10 minutes.

Pipe the dark chocolate into your serving dish, refrigerate for 10-15 minutes.

Then pipe the semi sweet chocolate mousse, refrigerate for 10-15 minutes.

Finally, pipe the white chocolate mousse. If you are not very particular about getting the perfect lines for your mousse, you do not need to refrigerate in between the layering. I didn't!

Do refrigerate the mousse for at east 6 hours, preferably overnight.

To serve, garnish with whipped cream and berries.