For the red velvet cake: Position an oven rack in the center of the oven, and preheat to 350 degrees F. Line an 8-inch square baking pan with foil, leaving an overhang on all sides. Coat the foil with cooking spray.
Whisk together the flour, granulated sugar, baking soda and salt in a medium bowl; set aside. Stir together the cocoa powder and 2 tablespoons very hot water in a small bowl until smooth; let cool slightly. Stir together the milk and vinegar in another small bowl, and let stand until thickened, 3 to 5 minutes.
Whisk together the oil, eggs and vanilla in a large bowl until smooth. Whisk in the food coloring and the cocoa mixture. Alternate whisking in the flour mixture in three additions and the milk mixture in two, starting and ending with the flour, until just combined. Pour into the prepared pan.
Bake until a toothpick inserted in the center comes out clean, about 30 minutes. Once the cake is cool enough to touch, press it down slightly to make the layer even. Place the pan on a cooling rack and let cool completely.
For the cheesecake: While the red velvet cake bakes, combine the gelatin with 2 tablespoons water in a small microwave-safe bowl, and set aside to soften, about 5 minutes.
Heat the granulated sugar and corn syrup over medium heat in a small skillet. Cook, swirling the pan but not stirring, until the mixture turns amber, 5 to 7 minutes. Remove the skillet from the heat, and carefully whisk in the cream and bourbon. (If the caramel seizes and hardens, continue to stir over medium heat until it melts and is smooth again.) Bring the mixture to a fast simmer, and cook until the caramel thickens enough to coat the back of a spoon, 3 to 4 minutes. Let cool to room temperature, stirring occasionally to help the caramel cool faster.
Beat the cream cheese with an electric mixer on medium-high speed in a large bowl until completely smooth, about 1 minute. Scrape down the side of the bowl. Add the cooled caramel, sour cream and confectioners' sugar, and beat on medium-high speed until incorporated and smooth, about 1 minute.
Microwave the gelatin until melted, stirring as needed, about 30 seconds. Add it to the cream cheese mixture, and beat on medium-high speed to combine, about 30 seconds.
Spread the cheesecake mixture over the red velvet cake in an even layer. Cover loosely with plastic wrap, and refrigerate until set, at least 2 hours.
Make the whipped cream: Beat the cream and confectioners' sugar together with an electric mixer at medium-high speed in a large bowl until medium peaks form. Spread the cream over the cheesecake.
Use the foil overhang to lift the bars out of the pan. Peel down the foil, and thinly trim the edges of the bars. Cut into 12 even rectangles, wiping the knife clean between cuts.
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