In a large bowl, combine the dry cake mix and oats. Cut in the peanut butter with a pastry blender until the mixture is well mixed but crumbly.
In a small bowl, whisk together the egg and milk. Add this to the peanut butter mixture and stir just until combined.
Measure out 1 1/2 cups of the mixture and set aside.
Press the remaining peanut butter mixture into the bottom of the prepared pan, forming a crust.
In a small bowl, beat the cream cheese with an electric mixer until fluffy and smooth, about 1-2 minutes.
Add the caramel topping and beat just until combined.
Spread the caramel mixture over the peanut butter layer in the pan.
Sprinkle the reserved peanut butter mixture over the cream cheese evenly.
Bake for 30 minutes or until the center is nearly set.
Cool on a wire rack.
To prepare the topping:
Pour the chocolate chips into a medium-size bowl and set aside.
Heat the heavy cream in the microwave for 30-40 seconds, until the cream is very hot but not boiling.
Pour the heated heavy cream overtop the chocolate chips, cover the bowl and allow it to sit for 3 minutes.
Stir the chocolate and cream mixture. If the chocolate is not completely melted, heat it in the microwave in 10 second intervals*, stirring between each time, continuing until the chocolate is completely smooth.
Drizzle the chocolate overtop the bars.
Allow the chocolate to set, then cut into bars.
Be sure to take your time melting the chocolate. Use just 10 second intervals and stir well between each time. If the chocolate gets too hot, it will harden, so be sure to take your time!