This recipe stands on the shoulders of Nigella Lawson's 'Buttermilk Birthday Cake' though it can't be said to be it.
250g plain flour
1½ teaspoons baking powder
½ teaspoon bicarb
¼ teaspoon salt
50g cocoa powder (dark, unsweetened, the real deal)
100g dark chocolate (70%, or near as damn it, cocoa solids) melted
200g Greek yogurt (this needs to be the authentic, thick strained stuff)
1½ teaspoons vanilla extract
125g unsalted butter (very soft)
200g caster sugar
3 large eggs.
2 x sandwich tins, lined and buttered
Icing and filling.
300g dark chocolate (70% see above) broken into pieces
250ml double cream
5 tablespoons greek yogurt
Preheat oven to gas 4 (180ºC).
Mix together, in a bowl, the flour, cocoa powder bicarb, baking powder and salt. Stir the vanilla extract into the yogurt.
Cream the butter and sugar together until light and fluffy. Add the eggs, one at a time, beating thoroughly after each (the last one may make the mixture curdle, but don't worry too much about that, it happens, the cake still rises). Stir in the melted chocolate until the whole is a dark chocolatey brown. Add about a third of the flour mix, stir in vigourously. Add about a third of the yogurt, combine. Continue in this way: flour, beat; yogurt, beat, until everything’s in. If it seems a bit solid add a little milk to loosen it. Pour into the prepared tins and bake for about 35 minutes. It’s done when it’s begun to shrink away from the sides of the tins, and/or a cake tester comes out clean.
Put the tins on a cooling rack until they are cool enough to handle without oven gloves, then turn the cakes out of the tins and onto the rack.
Once good and cold you can ice them. To make the icing, put the chocolate and cream in a saucepan, place on medium heat, and whisk – at times idly at others vigorously – with a hand-whisk until the chocolate has melted and combined with the cream. Leave it to cool a little (if you can stick your finger in and leave it there comfortably it’s cool enough). Take about a quarter of the icing from the pan and put it in a bowl. To this add the yogurt, this is your filling.
Put one of the cakes on the plate or stand you plan to serve the it on. Spread with filling. Place the other on top, and cover with the icing.
This is one of those cakes you can't really go wrong with. I've baked it in a saucepan before and it's still come out perfectly, and I have messed about with the yogurt quantities too, depending on how much I had. As with all recipes read it over a few times so you can get the shape of it in your head. Then get everything ready before you begin. This will allow you to go about calmly and make the whole thing fun rather than frustrating.
Note on sweetness: I love cake but am not a huge fan of sugar, if you prefer a sweeter filling and/or icing just add some powdered sugar to taste.
Let me know if you make it and how you get on.