To make St. Patrick's Day Baileys Cheesecake Bars, start by preheating your oven to 325 degrees and adding a large pan of water to your bottom oven rack.
Begin your cheesecake bars by adding your chocolate sandwich cookies to a food processor and pulse until pulverized. Combine the cookie crumbs, melted butter and sugar together in a mixing bowl and then pour the cookie mixture into a 9 x 13 baking pan lined with parchment paper. Using your fingers or a spoon, firmly press the cookies evenly on the bottom and sides of the baking pan to make your crust. Set aside.
In a large mixing bowl, beat softened cream cheese until creamy and then add in sugar and mix well. One by one, add in eggs and beat until each is incorporated before adding in the next one. Add in sour cream, salt, vanilla, all purpose flour and Baileys and continue mixing until you have a creamy filling. Transfer 1 cup of cheesecake filling evenly into two separate bowls and add light green food coloring to one bowl and regular green food coloring to the other. Mix the food coloring into the batter to combine.
Pour the white cheesecake filling on top of the cookie crust crust and smooth until even. Using a spoon, pour alternating lines of light green cheesecake filling and dark green cheesecake filling down the length of the cheesecake. Swirl the colors into the cheesecake filing using the back of knife (or a chopstick!) to create a beautiful swirl pattern being sure not to swirl all the way down the crust. The more swirls, the better..
Bake in oven for 50-55 minutes or until center is no longer wobbly. When baking time is done, turn off oven, open oven door and let your St. Patrick's Day Baileys Cheesecake Bars sit for one hour in the open oven. Remove from oven and refrigerate overnight before pulling up on parchment paper and removing from baking pan. Cut into squares and serve!