Preheat oven to 180°C (160°C fan-forced). Lightly grease a 20cm x 30cm slice tin and line with baking paper.
For the base, combine flour, cocoa, almonds, coconut and sugar together in a medium size mixing bowl, stirring until well combined. Add melted butter, stirring with a wooden spoon until mixture is well combined. Spoon mixture into prepared tin and press it down flat to create an even base. Bake in preheated oven for 15 minutes or until top begins to golden. Remove from oven and allow to cool.
For the filling, combine milk and butter together in a small saucepan and place over a low heat, until butter melts. Add essence, stirring to combine. Place icing sugar in a medium mixing bowl, add milk mixture, stirring until smooth and well combined. Pour over cooled base and place in refrigerator for 1 hour to cool.
For the topping, pour boiling water into a small saucepan off the heat, about a third full and sit a small bowl on top, making sure the bottom does not touch the water. Add chocolate pastilles, stirring occasionally until chocolate melts. Remove from heat and add oil, stirring to combine. Pour over cooled filling and place in refrigerator for 1 hour or until set.