Place all the ingredients for the crust into a food processor and process until combined well. It should be sticky.
Line an 8 by 8 baking dish with parchment paper. Spray the paper with olive oil cooking spray.
Press the crust base into the dish and press it evenly over the bottom of the dish.
Prepare the custard filling by adding all ingredients into a stand mixer and blend until smooth.
Spread this filling over the crust.
Prepare the chocolate layer by melting the chocolate and butter in a bowl over simmering water or microwave for 30 seconds stirring until smooth and no lumps.
Spread chocolate over the custard filling.
Refrigerate at least 2-3 hours before slicing.