Line a 9 x 13-inch baking pan with parchment paper and set aside. In a large mixing bowl, add the rice cereal and set aside.
In a microwave safe bowl or stovetop, combine your caramilk chocolate, peanut butter, and maple syrup, and heat until the chocolate has melted. Whisk together, until smooth.
Transfer the melted Caramilk mixture into the cereal and mix well, until combined. Transfer into the lined baking pan and press down until even and smooth. Place the pan in the refrigerator.
Prepare the frosting. In a microwave safe bowl or stovbetop, combine the Caramilk chocolate with the peanut butter and heat until the chocolate has melted. Whisk together, and pour over the slice mixture. If desired, melt the white chocolate and add swirls to the melted Caramilk/peanut butter topping. Place back in the refrigerator for at least two hours, to firm up.
Notes
TO STORE: Caramilk slice will keep well at room temperature, covered, for up to 2 weeks. Store it in the refrigerator if you'd like them to keep longer. TO FREEZE: Place the leftover slices in a ziplock bag and store them in the freezer for up to 6 months.