In a large skillet or saucepan, melt the butter over medium heat. Once melted and slightly foamy, pour over the corn flakes and toss to coat evenly. Stir frequently for 2–3 minutes until the flakes are lightly toasted and fragrant. This step enhances their crunch and flavor. Remove from heat and let cool slightly.

In a large mixing bowl, whisk together the peanut butter, maple syrup, vanilla, and salt until smooth and well combined. The mixture should be thick but pourable.

Add the buttered corn flakes to the peanut butter mixture. Using a spatula, gently fold until every piece is coated and the mixture looks evenly textured. Try not to crush the corn flakes too much—you want those flaky layers for a true Butterfinger crunch.

Line a 9x9-inch baking dish with a piece of parchment paper, leaving some overhang for easy removal. Pour the coated mixture into the pan and press it down firmly and evenly in a single layer with a spatula or the back of a measuring cup. Compacting it well will help the bars hold together once cut.

Place the dish in the freezer for about 1 hour, or until the mixture is solid enough to cut cleanly.

In a double boiler (or a heatproof bowl set over simmering water), melt the chocolate chips and coconut oil together. Stir frequently until the mixture is smooth and glossy. Remove from heat and let cool for 5 minutes so it slightly thickens. You could also melt chocolate in a microwave-safe bowl, stirring every 30 second intervals.

Remove the peanut butter mixture from the freezer and lift it out of the pan using the parchment paper. Using a sharp knife, cut into 20 rectangular bars (or larger pieces, if preferred). Using a fork or dipping tool, coat each piece fully in the melted chocolate, allowing excess chocolate to drip off before placing them on a cooling rack or parchment-lined baking sheet.

Once all the bars are coated, transfer them to the refrigerator for about 30 minutes (or the freezer for 15 minutes) until the chocolate is completely set and firm.