Start by lining a 9x9 inch square baking pan with aluminum foil, letting the foil overhang slightly for easy removal later. Lightly spray the foil with cooking spray.

In a food processor, blend whole Oreo cookies until they reach fine crumb texture. Melt unsalted butter and dark chocolate together in a microwave-safe bowl until smooth. Combine with cookie crumbs and press into the prepared pan.

Beat the brick-style cream cheese until fluffy. Melt the remaining dark chocolate with the heavy whipping cream over low heat, then combine with cream cheese, blending until smooth. Add Baileys or Kahlua and salt if desired.

Pour the filling over the crust, spreading evenly. Sprinkle mini chocolate chips across the top.

Cover the pan with plastic wrap and refrigerate for at least 3 hours, or overnight. Once set, slice into squares for serving.