Grease and line a 20 x 20 cm baking tin and set aside.
Process the biscuits in a food processor until fine crumbs and set aside.
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 tbsp instant coffee, 1 tbsp cocoa powder, 1 tbsp light brown sugar, 1 tbsp boiling water
Place sweetened condensed milk and butter in a large bowl and heat in the microwave until butter is melted, then mix to combine.
250 g sweetened condensed milk, 80 g salted butter
Mix in vanilla and coffee/cocoa mixture, then add desiccated coconut and crushed biscuits, mixing well to combine.
85 g desiccated coconut, ½ tsp 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 tsp instant coffee
Spread chocolate icing over the biscuit base and then place in the fridge to set.