Step 1

Line a  9 inch square pan with parchment paper, and set aside.

Step 2

Melt the butter in a large heatproof bowl over a saucepan of simmering water. Whisk in the sugar and cocoa powder. Remove from heat and slowly add in the egg while whisking vigorously. Return to heat and continue to cook for 1-2 minutes until the mixture is smooth and thickened.

Step 3

Add the graham cracker crumbs, shredded coconut, and chopped nuts. Using a fork mix until well combined and the mixture comes together.

Step 4

Pour the mixture into your prepared pan. Using the palm of your hand press the mixture into an even layer and refrigerate until firm.

Step 5

Meanwhile, make your filling. Using a stand mixer (or an electric mixer) add butter, custard powder and mint extract to a large bowl, beat until smooth and combined. Add icing sugar alternately with the milk, making 3 additions of sugar and 2 of milk. Spread the filling over the cooled base. Refrigerate until firm, approx. 1 hour.

Step 6

When the filling is firm make your topping. In a heatproof bowl over a saucepan of hot water, melt chocolate with butter until smooth. Pour the chocolate mixture over the filling and using an offset spatula spread the topping evenly over the filling. Refrigerate until chocolate is almost set, approx. 20-30 minutes. Then using a sharp knife slice into bars. See tips on how to cut Nanaimo bars.