Line a 9x9-inch pan with aluminum foil for easier cleanup and spray with cooking spray; set aside.

To the canister of a food processor, add the Oreos (whole) and process on high speed until you have fine crumbs; set aside.

To a small microwave-safe bowl, add the butter and 1 tablespoon dark chocolate. Heat on high power until the chocolate and butter have melted and can be stirred smooth.

Pour the melted chocolate and butter mixture into the food processor with the Oreo crumbs. Process on high speed to incorporate. Turn the crumb mixture out into the prepared pan and hard-pack the mixture to form an even, flat crust layer; set aside.

To a large mixing bowl, add the cream cheese and beat with a handheld electric mixer on high speed until fluffy; set aside.

To a separate, large, microwave-safe bowl, add the 8 ounces chopped dark chocolate and heavy whipping cream. Heat in 30-second increments until the chocolate has melted and can be stirred smooth into the cream, creating a silky mixture. This will likely take about 90 seconds total, but microwaves vary and you don't want to scorch the mixture.

Transfer the creamy chocolate mixture into the bowl with the cream cheese and beat on high power until smooth and combined.

Optionally add the Baileys Irish Cream or Kahlua and/or salt. The salt is highly recommended to complement the chocolate flavors and balance the richness.

Evenly spread the cheesecake filling mixture over the crust.

Evenly sprinkle with the mini chocolate chips. Refrigerate for at least 3 hours, or overnight, before slicing and serving. After the 3-hour chilling period, cover the pan tightly with plastic wrap.