Very closely adapted from Fiona Cairns (instructions are mine but ingredients are all hers, with exception of chocolate in icing)
Ingredients
Cake:
3½ oz 50-60% cacao semisweet chocolate, finely chopped
6 T boiling water
1⅓ cups AP flour
1 t baking powder
1 t baking soda
1 cup almond flour
¾ cup unsalted butter, softened
1⅓ cups packed brown sugar
1 t vanilla
3 large eggs, lightly beaten
½ cup buttermilk
Icing:
3 oz semisweet 50-60% cacao chocolate (can use up to 72% cacao if you prefer), chopped
3 T unsalted butter
1 T golden syrup (Lyle's Golden Syrup is what we would use in the States)
2 T packed brown sugar
½ cup heavy cream
Instructions
Preheat oven to 350 F. Lightly grease 2 8-inch round cake pans (see notes above about pan size) and line the bottom with parchment rounds. Grease again.
Place the chocolate in a bowl and pour the boiling water over it. Whisk it smooth and set aside to cool.
Sift together the flour, baking soda and baking powder. Whisk it with the almond flour and set aside.
Cream the butter and sugar until light and fluffy with a mixer, a good 5 minutes. Beat the vanilla into the eggs. Pour the eggs and vanilla slowly into the creamed butter with the mixer running. Add a tablespoon of the flour mixture to prevent curdling. Mix until nicely blended and then mix in the melted chocolate. Beat in the buttermilk. Fold in the flour mix gently.
Divide the batter between the pans. Bake for 30-35 minutes (25-30 minutes for 9-inch pans), or until firm to the touch. A toothpick inserted into the center should come out with a only a few crumbs attached, and, as you can see from the photo, the edges of the cake will pull away from the sides of the pan. And they will smell fantastic! Let the cakes cool in the pans for 2-3 minutes and then invert onto a cooling rack onto a piece of parchment paper. Let cool until cold before icing.
To make the icing, melt the chocolate and butter in the microwave on 50% power in 30 second increments until melted and whisked smooth. Stir in the syrup and sugar. Gradually pour in the cream, whisking, until whisked smooth and thickened. Set aside to cool.
To assemble the cakes--place the top side down and spread half of the cooled icing onto the cake. Let some drip over the sides. Place the other cake, once again top side down (because the bottoms are perfectly flat) and spread the remaining icing on top of the cake, once again letting some of it drip over the sides. I sprinkled my cake with pearl sprinkles to make it more festive.
Recipe by The Spiced Life at https://www.thespicedlife.com/bake-and-decorate-family-chocolate-cake/