Lightly spray a 9-inch springform pan with cooking spray. Pulse Oreo cookies in a food processor until fine crumbs. Combine crumbs with melted butter until it resembles wet sand. Press into the pan and freeze for 30 minutes to set.

In a heatproof bowl, place chopped chocolate. Heat heavy cream and Baileys in a saucepan until simmering, then pour over chocolate and let sit for 2 minutes. Whisk until smooth, then blend in butter, vanilla, espresso powder, and salt.

In a chilled mixing bowl, combine cold heavy cream and sifted confectioners' sugar. Beat with an electric mixer on medium speed until soft peaks form.

Pour the chocolate filling into the crust, smoothing the top. Cover with plastic wrap and refrigerate for at least 3 hours until set.

Remove from refrigerator, dollop whipped cream on top, and optionally sprinkle chocolate shavings for garnish.

Release the springform pan sides and slice into wedges. Serve immediately.