Add the Oreos to the bowl of a food processor and blitz until broken down into fine crumbs.
Transfer the crushed Oreos to a mixing bowl and pour in 1/3 cup + 1 tablespoon of melted butter. Stir together to combine.
Push the Oreo mixture into the bottom and all the way up the sides of a lightly greased, loose-bottom 9-inch tart tin. Take to time to get it nice and compacted and into a smooth, even layer.
Put the tin in the fridge and chill for at least 30 minutes.
Add the chocolate chips to a large mixing bowl.
Heat the cream and remaining 3 tablespoons in a saucepan on a medium heat, stirring frequently.
Once the mixture begins to boil, remove it from the heat and immediately pour it into the bowl with the chocolate chips.
Whisk together the cream mixture and chocolate chips until you have a smooth, shiny ganache.
Once the tart base has chilled for 30 minutes, remove it from the fridge and spoon the caramel into the bottom. Spread it out in an even layer with the back of a spoon.
Pour the chocolate ganache on top and gently smooth it out up to the edges of the tart crust.
Put the tart back into the fridge for at least 2 hours to set.
Optionally sprinkle the tart with a little flaky sea salt, then remove it from the tin and serve.