Brooklyn blackout cake

Brooklyn blackout cake

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(17 ratings)

Prep: 30 mins Cook: 30 mins - 40 mins plus cooling and over 5 hrs chilling

More effort

Cuts into 12 slices

This rich, dark sponge is filled and coated with a thick chocolate custard, then finished with crumbled cake - best eaten chilled

Nutrition and extra info

  • sponge only

Nutrition: per slice

  • kcal548
  • fat27g
  • saturates12g
  • carbs68g
  • sugars47g
  • fibre3g
  • protein7g
  • salt0.6g
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    For the cake

    • 140g unsalted butter, plus extra for greasing
    • 100ml vegetable oil
    • 140g buttermilk
      Buttermilk pancake mixture in bowl with whisk



      There are two types of buttermilk. Traditional buttermilk is a thin, cloudy, slightly tart but…

    • 100ml coffee, made with 1 tsp espresso powder
    • 2 large eggs, at room temperature



      The ultimate convenience food, eggs are powerhouses of nutrition packed with protein and a…

    • 1 tsp vanilla extract
    • 250g light muscovado sugar
    • 250g plain flour
    • 1 tsp bicarbonate of soda
      Bicarbonate of soda

      Bicarbonate of soda

      Bicarbonate of soda, or baking soda, is an alkali which is used to raise soda breads and full-…

    • 2 tsp baking powder
      Baking powder

      Baking powder

      bay-king pow-dah

      Baking powder is a raising agent that is commonly used in cake-making. It is made from an alkali…

    • 50g cocoa powder

    For the custard filling and covering

    • 250g golden caster sugar
    • 500ml full-fat milk



      One of the most widely used ingredients, milk is often referred to as a 'complete' food…

    • 140g chocolate, 85% cocoa solids, broken into cubes

      Chocolate ganache


      Chocolate ganache is a combination of chocolate and double cream. It's simple to…

    • 50g cornflour
    • 2 tsp espresso powder
    • 2 tsp vanilla extract


    1. Make the custard first as it needs to chill. Put all the ingredients, except the vanilla, in a large pan and bring gently to the boil, whisking all the time, until the chocolate has melted and you have a silky, thick custard. It will take 5-7 mins from cold. Stir in the vanilla and a generous pinch of salt, then scrape the custard into a wide, shallow bowl. Cover the surface with cling film, cool, then chill for at least 3 hrs or until cold and set.

    2. Heat oven to 180C/160C fan/gas 4. Grease then line the bases of 2 x 20cm sandwich tins. Melt the butter in a pan, then remove from the heat and beat in the oil, buttermilk, coffee and eggs. In a large bowl, whisk the dry ingredients togetherplus 1/4 tsp salt (saves sifting) and squish any resistant lumps of sugar with your fingers. Tip in the wet ingredients and whisk until smooth.

    3. Divide the batter between the prepared tins and bake for 25-30 mins until risen and a skewer inserted into the middle of the cakes comes out clean. Cool for 10 mins, then transfer to a rack to cool completely, parchment-side down.

    4. Remove the parchment linings from the cakes. If the cakes are domed, trim them flat. Now cut each cake across the middle using a large serrated knife. Put your least successful layer and any trimmings into a processor and pulse it to crumbs. Tip into a large bowl.

    5. Sit one layer on a cake plate and spread it with a quarter of the custard. Sandwich the next layer on top, add another quarter of the custard, then top with the final layer of cake. Spoon the remaining custard on top of the cake, then spread it around the top and down the sides until smooth. Chill for 15 mins to firm up the custard again.

    6. Hold the cake over the bowl containing the crumbs, then sprinkle and gently press a layer of crumbs all over the cake. Brush any excess from the plate. You’ll have some crumbs left. Chill for 2 hrs, or longer, before serving, and eat it cold. Can be made up to 2 days ahead. The cake gets fudgier and more enticing the longer you leave it.

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    Comments, questions and tips

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    Francis Smith
    18th Mar, 2020
    Not too difficult, and a perfect chocolate cake texture
    29th Jun, 2018
    Amazing recipe, amazing cake!
    11th Oct, 2017
    This is such a wonderful cake! I made it for my brother's birthday and it was loved by all! Super easy and quick to make but looked really impressive! We couldn't believe how soft and moist it was either! Beautiful and chocolatey but not overly sweet and the custard as icing was a nice change! Will be adding it to my archive of recipes and making it time and time again! :D
    18th Mar, 2017
    I've just made this cake for my husband's birthday and it is so, so good! I loved the use of custard instead of buttercream to layer it and I found the sponge very light (that's probably the buttermilk). It isn't hard to make, especially if you spread the process over two days like I did (made the custard on Thursday and the sponge on Friday). I found it did get even better the next day and I will definitely be making it again!
    30th Jan, 2017
    16th Jan, 2017
    Not the easiest cake to make, but not complicated in the least. It's a delicious chocolate cake and went down very nicely with sweet-tooths and savoury-lovers alike. It's not life-changing though - it is, in fact, just a chocolate cake. Although, the custard is definitely worth the effort. In fact, the custard is what makes it. The smell of the custard alone...
    3rd Apr, 2016
    Best chocolate cake I've made. Really nice cake. I also added some more chocolate and less sugar to the custard filling and was just right
    15th Jan, 2016
    This was relatively easy to make. The cake part is nice and light. Personally I found the custard way too sweet, although it does get better the longer you leave it in the fridge. I then used the custard recipe with some kids cupcakes I was making, but this time I cut the sugar down to 125g and I upped the chocolate to 200g. Great result ...seriously chocolatey and divine... for grown ups only, as it's far too good for kids!
    12th Dec, 2015
    I used 140ml of buttermilk as I guessed that was what was intended rather than the g listed in recipe. It turned out fine. As others have said, about a cup's worth of custard is left over after generously icing the cake inside and out. The cake is soft but was not difficult to slice into layers. It is very rich and should be served in thin slices. I wanted to like it...has all the ingredients I like - chocolate and more chocolate but something in the taste of the custard didn't make it wow for me...sadly won't be making it again.
    9th Nov, 2015
    Really Easy to make and tasted absolutely amazing, especially cold straight out of the fridge. Would 100% bake again


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