Place the chopped chocolate in a microwave-safe bowl or double boiler. Microwave in 30-second bursts, stirring after each, until smooth and glossy. The chocolate should be silky and fragrant.
Gently melt the butter in a small saucepan over low heat, just until it’s warm and melted without browning, then pour it into the chocolate and stir until combined. The mixture will be rich and shiny.
Add the honey or golden syrup and vanilla extract to the chocolate mixture if using, stirring well to incorporate. This adds a subtle sweetness and depth of flavor.
Pour the melted chocolate and butter mixture over the cornflakes in a large mixing bowl. Gently fold with a spatula until the flakes are evenly coated without crushing them, maintaining their crunch.
Line your 20x20cm pan with parchment paper, leaving overhang for easy removal. Transfer the mixture into the pan and press down firmly with the back of a spatula or spoon, creating an even, compact layer.
Let the bars set at room temperature for about 2 hours, or refrigerate for 1 hour until the chocolate is firm and shiny. You’ll notice the surface crack slightly when ready.
Once set, lift the entire block out of the pan using the parchment overhang. Use a sharp knife to cut into squares or rectangles, wiping the blade clean after each cut for neat edges.
Arrange the bars on a plate or tray. For an extra touch, drizzle with melted chocolate or sprinkle a pinch of sea salt on top before serving.
