This cheesecake is true decadence. Not for the timid or those who don't love dark chocolate and caramel. Do not look at the calorie count at the side of the page. This is a special occasion cake that will make chocolate lovers say OMG.
Mix the melted butter and oreo crumbs and press into the bottom of a 9 inch springform pan.
Mix the cream cheese with about 1 and 1/3 tins of condensed milk until smooth.
Microwave the chocolate chips and bittersweet chocolate for a minute or so until melted, stir to complete melting (make sure there are no unmelted lumps).
Mix the melted chocolate into the cream cheese mixture until evenly blended.
Add the eggs one at a time and mix (on low speed with electric mixer) to incorporate, try to avoid adding too much air to the mixture.
Pour mixture over the oreo crumbs in the pan and smooth the top.
Bake for 55 minutes, then remove from oven and run a knife around the side of the pan (this will help prevent the top from cracking).
Wait until the pan is cool to the touch then place on a serving plate and remove the outside of the springform pan.
Mix the milk and remaining 2/3 tin of the condensed milk in a large microwave safe bowl.
Add the caramels and microwave (stirring every minute) for several minutes until all the caramels are melted.
Stir caramel mixture until smooth and creamy then spread evenly over the top of the cheesecake.
When cheesecake is cool it should be refrigerated at least 4 hours before using, note the topping is better if the cheesecake is removed from the refrigerator 15 minutes or so before serving.
Alternative serving method: Refrigerate the cheesecake at least 4 hours without the topping; make the caramel topping just before serving; to serve, put some warm caramel topping on the plate, add a slice of cheesecake and drizzle caramel over the top.