Homemade shortbread for this recipe:
This recipe will make just under the required amount in this recipe, but it's perfect nonetheless, if you prefer homemade biscuits.

Ingredients:
60 grams / 2.11 ounces butter, room temperature
25 grams / 1/4 cup confectioner’s/icing sugar, sifted
80 grams / 1/2 cup plain flour
9 grams / 1 tablespoon corn flour

Directions:
Preheat oven to 190/375F and line a baking tray with greaseproof paper.

Beat the butter and sugar until pale and fluffy, approximately 4 minutes with a hand mixer on medium speed.

Add in the flour and corn flour and beat until the mixture is clumpy and no dry portions remain in the bowl - it will look like a rough dough.

Turn onto a lightly floured work surface and roll out to 1/2 inch thickness.

Cut into rectangles and place onto your baking tray.

Bake until golden on the edges and matte in appearance, approximately 14 minutes.

Remove and allow to cool fully.

Mix of chocolate: The reason for two different types of chocolate is due to the richness of the 70% chocolate and a chocolate with less cocoa is a little smoother on the palate.

Cutting and crumbling: Due to the butter and cream in this cake, it is quite usual for small pieces to crumble away as you cut, even with a hot knife, however, don't let that stop you from serving this, people will not care. Having made this several times, people are always always impressed.

Serving size: The richness of this happily serves a crowd in bite size, though some may go back for seconds.

Best served: This slice is best kept in the fridge when not serving due to the high butter content which will begin to melt the chocolate when it sits at room temperature for too long.

Adapted from Donna Hay Chocolate book