Line an 8-inch square baking pan with parchment paper, letting the edges overhang for easy removal.
In a saucepan over low heat, melt the butter and dark chocolate together, stirring gently until smooth and glossy, about 3-5 minutes. The mixture should be bubbling gently and smell rich.
While the chocolate mixture melts, toast the oats in a dry pan over medium heat for 2-3 minutes until they emit a nutty aroma and turn lightly golden, stirring often. This enhances their flavor and crunch.
Remove the melted chocolate from heat and stir in the honey, vanilla extract, and a pinch of salt until the mixture is smooth and evenly combined.
Pour the toasted oats into the chocolate mixture. Use a spatula to fold and stir until all the oats are thoroughly coated and sticky with the chocolate mixture.
Transfer the mixture into the prepared pan. Press it down firmly with the back of a spatula or your hands, smoothing the top and compacting the mixture to about 1.5-2cm thickness.
Refrigerate the pan uncovered for at least 2 hours, or until the slice is firm and set. For quicker results, you can freeze it for about an hour.
Once set, lift the slice out of the pan using the parchment overhang. Place on a cutting board and cut into squares or rectangles with a sharp knife, wiping the blade clean between cuts for neat edges.
Serve immediately or store in an airtight container in the fridge for up to 4 days. For longer storage, wrap tightly and freeze for up to a month. Enjoy the rich, chewy, and glossy treat!
