Line a 20x20 cm (9x9 inch) baking pan with parchment paper.
Pulse the digestive and corn flakes in a food processor or blender until finely ground.
Melt the butter in a pan. When butter is melted remove it from the heat and add peanut butter and powdered sugar. Whisk until smooth.
Add the grinded digestive and cornflakes. Mix until combined.
Spread evenly on prepared baking sheet.
Add caramel sauce on top of the cake mixture. Let it chill while you make the chocolate topping.
In a bain-marie melt chocolate and add 2 tbsp peanut butter. Spread evenly over the caramel layer. If you want to decorate with white chocolate do it now.
Refrigerate for at least 2 hours.
Cut into squares.
Notes
You can keep these bars in an airtight container in the refrigerator for up to 1 week.