Step 1: In a large saucepan, combine the granulated sugar and light corn syrup. Cook over medium heat, stirring frequently, until the sugar dissolves and the mixture just begins to boil.
Step 2: Remove the saucepan from the heat immediately. Stir in the creamy peanut butter and vanilla extract until the mixture is smooth and well combined.
Step 3: In a very large bowl, combine the Rice Chex cereal. Pour the warm peanut butter mixture over the cereal and stir gently with a spatula until all the cereal is evenly coated.
Step 4: Press the coated cereal mixture firmly and evenly into a greased 9x13 inch baking dish.
Step 5: In a microwave-safe bowl, combine the semi-sweet chocolate chips and butterscotch chips. Microwave in 30-second intervals, stirring well after each, until completely melted and smooth. Be careful not to overheat.
Step 6: Spread the melted chocolate and butterscotch topping evenly over the cereal mixture in the baking dish.
Step 7: Chill in the refrigerator for at least 1 hour, or until the topping is completely set. This is crucial for the perfect soft texture.
Step 8: Once set, cut the Scotcheroos into squares. Garnish with a dusting of powdered sugar or an extra chocolate drizzle, if desired, and serve.