Line a 9x9-inch tin with aluminum foil and set aside. Crush the digestive biscuits - but not too finely - and place in a heatproof bowl.
Combine unsalted butter, golden/maple syrup and cocoa powder in a pot and heat over very low heat, stirring constantly with a spatula/wooden spoon until butter is melted and cocoa powder has dissolved.
Pour the butter-syrup-cocoa mixture into the bowl of crushed digestive biscuits and stir until the biscuit pieces are well coated in the butter-syrup-cocoa mixture.
Spoon the mixture into prepared tin, pressing it down with the back of a spoon. Allow to cool then refrigerate for 30 minutes.
Place the chocolate in a heatproof bowl. Set the bowl of a pot of simmering water - do not let the water touch the bottom of the bowl. When almost all the chocolate has melted, remove the bowl from the pot and stir to melt the remaining chocolate. Let the chocolate cool slightly.
Poke some holes in the biscuit base and pour the melted chocolate over it, smoothing it out with a palette knife or the back of a spoon. Refrigerate until ready to serve.
Before serving, take it out of the fridge and let it rest for 10 minutes for the chocolate to soften. Lift up the biscuit block using the aluminum foil, and peel the aluminum foil away. Cut the biscuit block into 16 or 20 squares. Indulge and enjoy.