In a large bowl, beat the softened cream cheese until smooth and creamy. Gradually add in the powdered sugar and vanilla extract, mixing until fully incorporated.
In a separate bowl, whip the heavy cream to soft peaks using an electric mixer. Gently fold the whipped cream into the cream cheese mixture until light and fluffy to make the cheesecake layer.
Place the Rice Krispie cereal in a large mixing bowl. If desired, mix in the chopped walnuts.
Spread half of the Rice Krispie mixture evenly in the bottom of the prepared 9x9-inch pan, pressing gently to form a compact layer.
Drizzle half of the caramel sauce over the Rice Krispie base and spread evenly with a spatula or the back of a spoon.
Spoon the cheesecake mixture over the caramel layer and spread it out evenly with a spatula.
Add the remaining Rice Krispie cereal on top of the cheesecake layer, pressing gently to adhere. Drizzle the rest of the caramel sauce evenly over the top.
Melt the semi-sweet chocolate chips in the microwave in 20-second intervals, stirring between each, until smooth. Drizzle the melted chocolate over the top layer of bars in a zigzag pattern.
Refrigerate the bars for at least 3 hours or until firm enough to slice.
Once chilled, cut the bars into squares using a sharp knife. Serve chilled for the best texture and flavor.