Line your baking pan with parchment paper, leaving some overhang for easy removal.
Place the butter in a saucepan over low heat and gently melt, stirring occasionally until it shimmers and becomes smooth.
Add the chopped semi-sweet chocolate to the melted butter and stir continuously until the mixture is completely melted and glossy, releasing a rich chocolate aroma.
Stir in the honey (or corn syrup) and vanilla extract until the mixture is smooth and uniform, about 1 minute.
Pour in the crispy cereal and gently fold it into the chocolate mixture with a silicone spatula until evenly coated and fragrant.
Transfer the mixture into your prepared pan and press it down firmly with the spatula to create an even layer. Let it crack slightly under pressure—that's a good sign.
Sprinkle a pinch of flaky sea salt on top, if desired, to enhance the chocolate flavor.
Refrigerate the pan uncovered for at least 1 hour, or until the bars feel firm and hold their shape when gently pressed.
Use a sharp knife to cut the set mixture into squares or rectangles, wiping the blade clean between cuts for neat edges.
Serve immediately or store the bars in an airtight container in the fridge for up to 5 days for best crunch.
