Preheat your oven to 350 degrees Fahrenheit. This is essential to ensure the crust bakes evenly. Prepare a 9x13-inch baking pan by lining it with heavy-duty aluminum foil, leaving a 2-inch overhang on two sides. This will make it easier to lift the bars out later. Lightly spray the foil with nonstick baking spray to prevent sticking.
In a large bowl, combine the crushed Oreo cookies with the melted butter. Mix well until the crumbs are fully coated. The mixture should resemble wet sand. Press this mixture firmly into the bottom of the prepared pan, making sure to cover the entire surface and slightly up the sides.
Place the crust in the preheated oven and bake for 10 minutes. This will help set the crust, giving it a firm base for the creamy filling. Once done, remove it from the oven and set it aside on a cooling rack.
Now, decrease the oven temperature to 325 degrees Fahrenheit. In the bowl of a large food processor, combine the cream cheese and sour cream. Pulse until completely smooth, scraping down the sides as necessary. This ensures a silky filling without lumps.
Add the granulated sugar, vanilla extract, and espresso powder to the mixture. Blend until everything is well combined and smooth. The espresso powder enhances the flavor, so don’t skip this step!
On low speed, add the eggs and egg yolks one at a time, mixing gently to avoid overmixing. Overmixing can lead to cracks in your cheesecake, so mix just until combined.
Using a rubber spatula, carefully fold in the Baileys Irish cream until it’s just incorporated. Follow this by folding in the all-purpose flour. Be gentle to maintain the lightness of the batter.
Pour the cheesecake filling over the cooled crust, spreading it evenly with the spatula. The filling should look smooth and creamy, ready for baking.
Ensure your oven has cooled to 325 degrees Fahrenheit, then carefully place the pan inside. Bake for about 40 minutes, or until the edges are set but the center is still slightly jiggly. This ensures a creamy texture.
Once baked, turn off the oven, crack the door, and let the cheesecake cool in the oven for 10 minutes. This gentle cooling helps prevent cracks.
Remove the cheesecake bars from the oven and transfer them to a wire rack to cool to room temperature. For best results, refrigerate them for at least 4 hours, or overnight, to allow the flavors to meld.
Now for the ganache! Place the chopped chocolate in a large bowl. In a small saucepan, heat the heavy cream over medium heat until it just reaches a rolling simmer. Immediately remove from heat and pour the hot cream over the chocolate. Let it sit for 1 minute.
Using a whisk, stir the chocolate and cream together until you achieve a smooth, glossy ganache. Stir in the remaining Baileys Irish cream. Set this aside to cool until it's tepid.
Carefully pour the ganache over the cooled cheesecake, spreading it evenly with a spatula. Let it set but remain creamy, about 1 hour.
When you’re ready to serve, use the foil overhang to lift the cheesecake bars from the pan. Transfer them to a cutting board. Using a large, sharp knife, slice into squares, wiping the knife clean between slices. Serve and enjoy your delicious creation!