In a food processor, pulse the Oreo cookies until finely ground. Transfer to a bowl and add the melted butter. Mix until well combined.

Place the mixture into a 9-inch tart pan and press against the bottom and sides. Freeze while making the filling.

Place dark and milk chocolate in a medium bowl. Set aside.

In a medium saucepan, heat heavy cream without allowing it to boil. Remove from heat and pour over the dark and milk chocolate. Let it sit for a minute before stirring.

Add the butter and brown sugar to the mixture and stir until fully combined, and smooth.

Pour over the chilled oreo crust. Smooth the top using with an angled spatula or the back of a spoon. Refrigerate for at least 4 hours, preferably overnight.

Serve with fresh raspberries or chopped nuts.