Welcome to Nigella

Ingredients

FOR THE CAKE:

• 200g plain flour
• 1/2 teaspoon bicarbonate of soda
• 50g cocoa
• 275g caster sugar
• 175g soft unsalted butter
• 2 eggs
• 1 tablespoon real vanilla extract
• 80ml sour cream
• 125ml boiling water
• 175g dark chocolate chips (unless you'd prefer milk)

FOR THE SYRUP:

• 1 teaspoon cocoa
• 125ml water
• 100g caster sugar
• 25g dark chocolate (from a thick bar if possible)

Method

1. Take whatever you need out of the fridge so that all ingredients can come to room temperature.
2. Preheat the oven to gas mark 3/170°C, putting in a baking sheet as you do so, and line a 900g loaf tin (mine measures 21x11cm and 7.5cm deep and the cooking times are based on that) with greased foil - making sure there are no tears - and leave an overhang all round. Or use a silicon tin.
3. Put the flour, bicarb, cocoa, sugar, butter, eggs, vanilla and sour cream into the processor and blitz till a smooth, satiny brown batter. Scrape down with a rubber spatula and process again while pouring the boiling water down the funnel. Switch it off then remove the lid and the well-scraped double-bladed knife and, still using your rubber spatula, stir in the chocolate chips or morsels.
4. Scrape and pour this beautiful batter into the prepared loaf tin and slide into the oven, cooking for about 1 hour. When it's ready, the loaf will be risen and split down the middle and a cake-tester, or a fine skewer, will pretty well come out clean. But this is a damp cake so don't be alarmed at a bit of stickiness in evidence; rather, greet it.
5. Not long before the cake is due out of the oven - say when it's had about 45-50 minutes - put the syrup ingredients of cocoa, water and sugar into a small saucepan and boil for 5 minutes. You may find it needs a little longer: what you want is a reduced liquid, that's to say a syrup, though I often take it a little further, so that the sugar caramelizes and the syrup has a really dark, smokey chocolate intensity.
6. Take the cake out of the oven and sit it on a cooling rack and, still in its tin, pierce here and there with a cake tester. Then pour the syrup as evenly as possible, which is not very, over the surface of the cake. It will run to the sides of the tin, but some will have been absorbed in the middle.
7. Let the cake become completely cold and then slip out of its tin, removing the foil as you do so. Sit on an oblong or other plate. Now take your bar of chocolate, wrapped in foil if you haven't got much of its wrapper left, and cut with a heavy sharp knife, so that it splinters and flakes and falls in slices of varying thickness and thinness.
8. I've specified a weight, but really go by eye: when you think you've got enough to scatter over the top of the loafcake, stop slicing. Sprinkle these chocolate splinters over the top of the sticky surface of the cake.