Line your square dish with parchment paper, leaving some overhang for easy lifting later.
Chop the dark chocolate into small, even pieces to help it melt faster and more smoothly.
Place the chopped chocolate into a heatproof bowl and melt it over a pot of simmering water, stirring gently until silky and glossy. This should take about 3-4 minutes.
While the chocolate melts, crush the biscuits into fine crumbs, aiming for a mix of powder and small chunks for texture.
Remove the melted chocolate from heat and stir in the butter or coconut oil until fully combined and shiny. Add honey or syrup if using, and mix well.
Gently fold the crushed biscuits into the melted chocolate mixture until evenly coated and sticky.
Pour the mixture into the prepared dish and use a spatula to spread it evenly, pressing down firmly to compact everything tightly.
Refrigerate uncovered for at least 3 hours, or overnight for best results, until the mixture is firm and set.
Lift the set block out of the dish using the parchment overhang and place on a cutting board.
Use a sharp knife to slice the block into even bars or squares, wiping the knife clean between cuts for neat edges.
Serve immediately or store in an airtight container in the fridge for up to 5 days. Enjoy the rich, crumbly, chocolatey goodness!
