Prep the pan. Line your pan with parchment, leaving some overhang for lifting. Lightly grease the parchment and sides to prevent sticking.

Measure the cornflakes. Add 6 cups to a large mixing bowl. Use a bowl big enough to toss everything without crushing the cereal too much.

Heat the syrup and sugar. In a medium saucepan, combine corn syrup (or honey) and sugar. Warm over medium heat, stirring often, until the sugar fully dissolves and the mixture just begins to bubble. Do not let it boil hard—that can make the bars too hard.

Stir in peanut butter. Remove from heat and add the peanut butter, vanilla, and salt. Stir until smooth and glossy. Taste for salt and adjust if needed.

Combine with cornflakes. Pour the warm peanut butter mixture over the cornflakes. Use a silicone spatula to gently fold until every flake is coated. Work quickly before it firms up.

Press into the pan. Transfer the mixture to the prepared pan. Lightly grease your hands or the back of a spatula and press evenly into the corners. Don’t press too firmly or the bars can become dense.

Optional chocolate finish. Melt chocolate chips in short bursts in the microwave or over a double boiler. Drizzle over the top. Add flaky sea salt if you like a sweet-salty pop.

Let set. Allow the bars to cool at room temperature for 45–60 minutes, or pop them in the fridge for 20–30 minutes until firm enough to slice.

Slice and serve. Lift the slab out with the parchment and cut into squares or rectangles with a sharp knife. Wipe the blade between cuts for clean edges.