¼teaspoonfine sea salt(increase salt to ½ teaspoon if using unsalted butter)
5tablespoons(30 g) unsweetened cocoa powder
3tablespoonsgranulated sugar
1teaspoonpure vanilla extract
1largeegg
2cups(225 g) graham wafer crumbs (from about 30 graham wafer squares 2¼"x 2½" each/5.5 x 6 cm)Use gluten-free graham wafers or other crisp gluten-free cookies, crushed, for a gluten-free version.
1cup(90 g) unsweetened medium-shredded coconut
½cup(50 g) finely chopped walnuts
Icing:
½cup(115 g) salted butter, softened
2 tablespoons(30 ml) heavy cream, room temperature(or use milk)
2½tablespoonscustard powder(like Bird's®, or substitution, see Notes)
4 oz.(115 g/4 squares) semi-sweet chocolate(or a scant ⅔ cup semi-sweet chocolate chips)
1oz.(28 g/1 square) unsweetened chocolate
1tablespoonbutter
Instructions
To make the base:
Grease a 9x9-inch square pan (22.5x22.5cm) liberally with butter. Line the bottom with a square of parchment paper cut to fit.
Put butter, cocoa powder, sugar, vanilla, salt, and egg into a glass or metal bowl and set on top of saucepan of simmering water to make a double boiler. Cook, whisking constantly and scraping down the sides of the bowl often, until the mixture is hot and forms a thick custard. This will take 5-6 minutes (or until it reaches about 160℉/71℃ on a thermometer).
Remove from the heat and stir in the graham wafer crumbs, coconut, and walnuts until everything is evenly coated in chocolate. The mixture will be thick - it may be easier to mix it with your hands than a spoon.
Pack the mixture into the greased baking pan and press it down evenly, using your hands or the smooth bottom of a measuring cup or glass. Allow the base to cool completely before adding the icing.
Make the icing:
Cream the butter, cream, custard powder, and icing sugar with an electric mixer or vigorously by hand. Use low speed until all the ingredients are combined, then increase the speed to medium-high and beat the icing until it is light in colour and fluffy (2-3 minutes).
Spread the icing evenly over the cooled chocolate/wafer base in the pan, smoothing the top evenly. Chill for 10 minutes (but no longer) while you are making the glaze.
Make the glaze:
Melt together the semi-sweet chocolate, unsweetened chocolate, and butter in the microwave or in a double boiler. Stir until smooth, and let cool for 5 minutes.
Pour over the icing layer and smooth the top, making sure to bring right to the edge of the pan all the way around. Let it set at room temperature or in the refrigerator.
Cut into 18 bars (3 rows of 6 bars). If the pan of bars is chilled, let it come to room temperature for at least 30 minutes before cutting, or the chocolate glaze layer will crack and shatter while cutting.
Notes
These bars are best served at cool room temperature, so that the top glaze layer is soft enough to bite into without shattering, but the center icing layer is still firm enough to hold its shape and be stable.To crush graham wafers, break them in pieces and grind them in a food processor or mini-chopper (in batches), or place them in a heavy-duty zip-top plastic bag and crush them with a rolling pin or the bottom of a heavy saucepan.SUBSTITUTIONS:If you don't have custard powder, you can substitute it with an equal amount of cornstarch (2½ tablespoons) and replace 1 teaspoon of the cream in the icing with 1 teaspoon of vanilla plus a pinch of salt and a pinch of turmeric (the turmeric is optional, but it makes the icing layer the traditional yellow colour without adding strong flavour).Any crisp cookies can be used to make the crumbs, and gluten-free graham wafers or cookies can be used to make the recipe gluten-free.Finely chopped pumpkin seeds or sunflower seeds can be used instead of walnuts to make the bars nut-free.You can omit the unsweetened chocolate in the glaze or substitute it with more semi-sweet chocolate.