In a small saucepan, add Butter (1/2 cup), Sweetened Condensed Milk (3/4 cup), Golden Syrup (2 tablespoon) and Instant Coffee (1 tablespoon). Stir over low heat until smooth.
In a large mixing bowl, add Graham Crackers (250 gram) and Walnut (1 cup). Stir together.
Combine wet and dry ingredients.
Transfer the batter into a lightly greased 30-centimeter by 20-centimeter slice pan, lined with non-stick baking paper. Make sure the surface is smooth and even.
Chill in fridge for about 1 hour, or until it sets.
For the chocolate layer, combine Dark Chocolate (200 gram) and Vegetable Oil (1 tablespoon) in a microwave-safe bowl. Heat for 30 seconds, stir, and repeat until chocolate is melted and smooth.
Pour the chocolate mixture over the cake and smooth the surface.
Chill in fridge for another hour, until the chocolate is set.
Slice into bars. Serve and enjoy!