Step 1

Grease a 9 x 9" pan and line with parchment.

Step 2

Place 1/2 cup butter, 1/4 cup sugar, and 3 Tbsp cocoa powder into a large, heatproof bowl over a pot with simmering water. Whisk until combined.

Step 3

Slowly pour in egg while whisking vigorously. Add vanilla. Continue whisking over simmering water until mixture has thickened and resembles a pudding.

Step 4

Remove mixture from heat and stir in graham cracker crumbs and coconut.

Step 5

Spread mixture evenly into the bottom of your 9x9 pan. Press down firmly to pack in. Chill in fridge while making custard.

Step 6

Cream together butter and powdered sugar, add in custard powder and milk and beat until smooth.**

Step 7

Spread evenly over base layer and return to fridge. Chill for 30mins.

Step 8

Place chopped chocolate and butter in to a microwave safe bowl. Microwave for 30 seconds, stir. Continue microwaving in 10 second intervals, stirring in between, until chocolate has melted.

Step 9

Spread evenly over custard layer. Chill in fridge until set (about 1 hour).

Step 10

Cut with a hot serrated knife.