This sweet is popular among Thai food bloggers..
Make the crust,put the oreo in a zip-lock bag and finely crumble it using a rolling pin. Transfer the crumb into a bowl and pour the melted butter over, mix until blended. Pour the crust mixture into an 8" springform tin ( or loose-based tin) and press them down evenly and tightly.Let it set in the fridge while making the filling.
Make the mousse filling, in a medium saucepan, add the milk and gelatin, stir and leave for a few minutes to let them absorb each other, then heat it gently on medium heat until the gelatin has dissolved. Remove the pan from the heat and add the white chocolate into the milk mixture, stir until the chocolate has melted and incorperated. Leave to cool at the room temperature, stirring from time to time, until the mixture reaches a sweetened condense milk-like texture.( To speed this stage up, you can either put it into the fridge or over a bowl of iced water )
In a mixing bowl, whip the cream to the soft peak,then pour the chocolate mixture into it, fold gently until everything blended. Stir in the oreo cookies. Take the curst out of the fridge and pour the mousse mixture over the crust evenly. Leave to set in the fridge (preferrably)overnight. Then gently unfold the pie and decorate as you wish before serving.