Line a 13x9 pan with aluminum foil. Grease the bottom and sides of the pan with butter.
Melt 1 cup of butter. With an electric mixer, beat the melted butter, sugar and eggs. In a small cup or bowl, dissolve 2 tbsp of instant coffee with 1 tsp of water. Add the dissolved coffee crystals to the mixture. Beat in the cocoa powder, Oreo cookie crumbs and coconut.
Press the mixture into the pan so that it is even and flat.
Bake in a 350F oven for 15 minutes. Cool on a wire rack for 10 minutes. Chill in the fridge for at least 20 minutes.
To make the filling, beat the 1/2 cup butter with the icing sugar and custard powder. In a small cup or bowl, dissolve 2 tbsp of instant coffee with 1 tsp of water. Add the dissolved coffee crystals to the filling mixture. Beat in the cream. The filling should become creamy and smooth.
Spread the filling evenly across the base and chill for another 30 minutes.
Melt the chocolate chips with the 2 tbsp butter. Spread the chocolate accross the filling layer. Chill until set, then cut into bars using a hot dry knife.