In a medium saucepan, melt the butter over low heat. Add the marshmallows and stir until completely melted and smooth.

Remove from heat and stir in the vanilla extract.

In a large mixing bowl, combine the melted marshmallow mixture with the Rice Krispies. Stir until well coated.

Fold in the apple pie filling, cinnamon, and walnuts (if using) into the Rice Krispie mixture until evenly distributed.

Press the mixture into a greased 9x9 inch baking dish evenly.

Allow the mixture to cool at room temperature for about 10 minutes, then refrigerate for 15 minutes to set.

Cut into squares, drizzle with caramel sauce, and serve with whipped cream.