Prepare the chocolate mixture
In a saucepan over medium heat, combine warm milk, cocoa powder, sugar, coffee powder, and dark chocolate. Stir continuously until the chocolate melts and everything is fully dissolved and smooth.

Add butter for richness
Turn off the heat and stir in the butter until fully melted and incorporated. Let the mixture cool slightly — it should still be warm but not too hot to dip biscuits.

Layer the biscuits
In a square or rectangular dish, begin layering by dipping each Marie biscuit into the warm chocolate mixture for about 1–2 seconds, just enough to soften but not break. Place them in a single layer to cover the bottom of the dish.

Add chocolate sauce between layers
Spoon some of the remaining chocolate mixture over the biscuit layer, smoothing it out evenly.

Repeat the layers
Continue layering dipped biscuits and chocolate mixture until you run out of ingredients, ending with a generous layer of chocolate on top.

Garnish and chill
Sprinkle crumbled biscuits on top for texture (optional). Cover and refrigerate for at least 4 hours, or overnight for best results.

Serve chilled
Slice into squares and serve cold. Each bite should be soft, rich, and slightly crunchy.