Grease a 6 " spring form pan lightly with butter.

Crush Oreo cookies along with their cream in ziplock bag with the help of rolling pin or in a food processor. Add melted butter and let it mix well.

Put this mixture into the pan. Spread and press evenly with the back of a spoon. Refrigerate till our chocolate mousse mixture is prepared.

Soak agar agar in water. Mix well so that no lumps are seen and keep aside.

Heat fresh cream in a pan till it starts to bubble then add chopped milk chocolate and let it sit for 2-3 minutes. Gently mix. Let the chocolate melt completely. U can easily do this in a microwave.

Let this mixture cool and come to room temperature.

Melt agar agar in microwave or on stove top till the it is fully mixed and no tiny specks can be seen and till it becomes transparent. Add this mixture to the chocolate mixture.

In a bowl beat chilled whip cream till stiff peaks.

Fold together chocolate mixture and whip cream together till fully incorporated. Be careful to not to deflate the whip cream.

Pour this mixture in the spring form pan. Spread evenly. Cover with cling wrap and refrigerate till 2-3hours.

Now we will prepare our white Mousse.

Repeat the same process to make white chocolate as we did for milk chocolate mousse.

Pour it over the set milk chocolate mousse. Spread evenly. Again cover with cling wrap and refrigerate for 4-5 hours or overnight.

Once set run a sharp knife around the edges and open the side of the pan.

Slide the side ring gently by placing the pan over a tall can.

Gently run a spatula under the crust of Oreo cookies and slide over serving dish