Grease and line a 20 x 20 cm baking tin and set aside.
Process the biscuits in a food processor until fine crumbs.
250 g Arnott's Marie biscuits
In a small bowl, mix together the instant coffee, cocoa powder and light brown sugar with boiling water to dissolve.
1 tablespoon instant coffee granules, 1 tablespoon cocoa, 1 tablespoon light brown sugar, 1 tablespoon boiling water
In a large bowl, place crushed biscuits, condensed milk, desiccated coconut, melted butter, vanilla and coffee/cocoa mixture and mix well to combine.
250 g sweetened condensed milk, 85 g desiccated coconut, 80 g salted butter, ½ teaspoon vanilla
Press the mixture into the greased and lined baking tin.
For the icing, melt the milk chocolate and butter together in the microwave (in 30 second bursts, mixing with a metal spoon between bursts). When melted, mix to incorporate the butter, then add instant coffee and mix well.
180 g milk chocolate, 40 g salted butter, ½ teaspoon instant coffee granules
Spread chocolate icing over the biscuit base and then place in the fridge to set.