Brooklyn Blackout Cake

I’ve been looking for an excuse to make a big chocolate cake (more than just wanting to eat a big chocolate cake) and finally it came in the form of a baking day at work. Everyone in the office needed to bring in something different, so here was my chance to attempt this incredible cake. This amazing recipe comes from one of the Hummingbird bakery cookbooks – which I’ve become slightly obsessed with, and after looking around on their website for advice on it I found that they’d described it as one of their more challenging bakes…excellent!

There were a few different techniques during this, making the custard was definitely a challenge – not to mention whisking it was a workout in itself! From reading about this cake it seems that there can be a few elements that might not work first time, so I think I was lucky with it really.


For the cake

  • 100g unsalted butter, at room temperature
  • 260g caster sugar
  • 2 eggs
  • 1/4 teaspoon vanilla extract
  • 45g cocoa powder
  • 3/4 teaspoon baking powder
  • 3/4 teaspoon bicarbonate of soda
  • a pinch of salt
  • 170g plain flour
  • 160 ml whole milk

For the chocolate custard

  • 500g caster sugar
  • 1 tablespoon golden syrup
  • 125g cocoa powder
  • 200g cornflour
  • 85g unsalted butter
  • 1/2 teaspoon vanilla extract


  1. Preheat the oven to 170C/325F/Gas mark 3. Line 3 20cm cake tins (the original recipe asked for 3 layers, but I chose to do 2 thicker layers, and added a little more cooking time)
  2. Put the butter & the sugar in a mixer (with a paddle attachment) and cream until light & fluffy. Add the eggs one at a time, making sure to scrape any mixture from the sides of the bowl until its all mixed well.
  3. Turn the mixer down to slow, and beat in the vanilla, cocoa, baking powder, bicarbonate of soda and salt until mixed well.
  4. Add half the flour to the mixture, then all the milk, then the rest of the flour, and mix well.
  5. Pour the mixture into the prepared tins and level with a palette knife. Bake in the oven for 25-30 minutes. Remove from the oven after this time and leave the cakes in their tins for 5 minutes, then remove and place on a cooling rack.

For the custard

  1. Put the sugar, golden syrup, cocoa and 600ml of water in a large pan and bring to the boil over a medium heat, whisking every so often.
  2. Mix the cornflour with 120-200ml of water, whisking briskly as you add the water. It should become the consistency of thick glue (add a little more water if too thick but don’t exceed 200ml). Whisk this gradually into the cocoa mixture into the pan over a medium heat. Bring back to the boil whisking constantly. Cook for a few minutes whilst whisking, until quite thick.
  3. Remove from the heat and stir in the vanilla and butter. Pour into a bowl and cover with clingfilm and chill until very firm (I spread my custard onto a tray and covered it as it chilled quicker this way).
  4. Once cool, slice a layer from one of the cakes and blitz in a food processor until it becomes fine crumbs.
  5. Spread some of the custard over the top of one of the cakes, then place another over it. Spread some more of the custard on this and top with the final cake. Then use the rest of the custard to cover the entire cake and sides. Cover the top and sides with the crumbs and chill in the fridge for at least 2 hours. Keep in the fridge until an hour before serving.

Overall this recipe was easier than I thought, but still more challenging than the usual things I’d bake. And it looks so impressive when it’s finished! Have to say there were some big fans of this when I brought it to work – it didn’t last very long!
We’d love to know if you try it and how you found the recipe.

Nat x





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