Preheat oven to 350°F (175°C). Line a 9x13 inch pan with foil and spray with cooking spray.
In a large bowl, combine the red velvet cake mix, 1 egg, and softened butter. Mix until a thick cookie dough forms. Press this mixture evenly into the bottom of the prepared pan.
In a separate bowl, beat the cream cheese until smooth. Add the granulated sugar and beat until smooth. Mix in the second egg, sour cream, and vanilla extract until no lumps remain. Gently stir in the mini chocolate chips.
Pour the cheesecake filling evenly over the red velvet crust. Bake for 30-40 minutes, or until the edges are set and the center is still slightly jiggly. The cheesecake will continue to set as it cools.
Let the bars cool completely to room temperature, then chill in the refrigerator for at least 4 hours, or preferably overnight, before slicing into bars.
Notes
These bars are best stored in an airtight container in the refrigerator for up to 5 days. They can also be frozen for up to a month.