Preheat oven to 350°F (175°C). Lightly grease a 15"x 10" jellyroll pan. If you like, line the pan with parchment paper and lightly grease the paper.
Combine the oats, brown sugar, flour, butter, and egg. Transfer to the prepared pan. Press firmly and evenly onto the bottom of the pan.
Bake 12 minutes. Then, set the pan on a wire rack to cool for 10 minutes.
Place the corn syrup, sugar, and peanut butter in a large microwave-safe bowl. Heat in the microwave in 30-second intervals until the mixture is melted and smooth. Stir every 30 seconds.
Stir in the cereal. Transfer the mixture to the crust. Working quickly, spread evenly and press firmly over the crust.
Place the chocolate chips and peanut butter chips in a microwave-safe bowl. Heat in the microwave at half power in 30-second increments until the chips melt when stirred. Stir until smooth and blended.
Spread evenly over the cereal layer. Sprinkle with the nuts and toffee bits.
Allow to cool completely before cutting into bars.
Notes
Store in an airtight container at room temperature up to 3 days.
For tips, step-by-step photos, and extra details, be sure to read the full post above before starting. It’s packed with helpful info to answer common questions!