Banana Boston Cream Cake

This weekend I let my Mum choose the bake! It is her birthday on Tuesday but I am away with work so I made her celebration cake for the weekend. recently bought a second-hand Humming Bird bakery book from Amazon for only around £3.00! It is possibly the best recipe book I have had. There is such a wide variety of cakes, cupcakes, traybakes in there to keep anyone occupied for many weekends! This week, this is where the cake is inspired from.


Truth be told, I had never heard of a Boston Cream Cake before, but when both I and my Mum saw custard in a cake, we were sold! After doing a little research I worked out what the stateside cake is, and for starters, it isn’t cream. The cake is a usually two sponges sandwiched together with custard. It is then finished with a chocolate glaze and is either left bare or decorated with sprinkles. This recipe has a banana twist which is incorporated in the sponge. For me, this is great, I remember simple desserts of banana and custard when we were younger. So to put it simply- this weeks post is a banana, custard, chocolate cake- a dream right?

Baking the cake itself was a little more complicated than some of the previous bakes I have posted on here, but fear not, it is still simple enough for anyone to do! Just make sure you read the steps carefully and do not try and jump ahead and incorporate the ingredients all together! Take your time with custard too! One thing I would also keep in mind is that the batter may seem a little stiff and almost as if it’s turning into a dough. I panicked when I saw this and was convinced it was game over. It’s really not. The sponge still comes out light and fluffy so just trust the recipe on this one! As there are many extras following baking the sponge make sure it is fully cooled too before you start assembling

23316039_10212932229952920_546852985_n.The one issue I did find and am yet to solve is when sandwiching the cakes together how to get the ganache to fill the gaps and make the cake look more aesthetically pleasing and covered. As you may see from some of the photos there are gaps where the ganache hasn’t filled the cake. If anyone has any advice for this it would be much appreciated. I want to be honest about where I go wrong on my bakes or what I don’t know as that way it’s helpful for everyone! This blog is for the everyday baker, so if I get it wrong I want others to know that if they do too, it’s okay, it’s how you learn!

Adapted from the humming bird bakery




  • 100g Unsalted Butter/Margarine
  • 150g Caster Sugar
  •  2 Large Eggs
  • 1 Medium Banana
  • 125g Soured Cream
  • 1 Tsp Vanilla Extract
  • 300g Plain Flour
  • 3/4 Tsp Baking Powder
  • 1 Tsp Bicarbonate of Soda

Custard Filling

  • 250ml Whole Milk
  • 1 Tsp Vanilla Extract
  • 3 Eggs Yolks
  • 50g Caster Sugar
  • 15g Plain Flour
  • 15g Corn Flour

Chocolate Ganache

  • 400ml Double Cream
  • 400g Dark Chocolate

And a little chocolate left over for decoration, I also had edible glitter



  1. Preheat the oven 170 degrees and line two sandwich cake tins with baking paper, I used two 7 1/2 inch tins but the recipe advised 8-inch tins. I’d say, use what you got that’s roughly around this size!
  2. Using an electric hand whisk cream together the butter and sugar until it resembles something a little like scrambled egg!
  3. Whisk in the eggs one at a time into the creamed butter until well incorporated
  4. Mash the banana up either using a fork in a bowl or a potato masher on a chopping board, add this to a jug with the soured cream and mix well.
  5. In a seperate bowl sift the flour, baking powder and bicarbonate of soda. You should have 3 separate bowls/jugs of ingredients.
  6. With the electric mix on a slow heat mix the banana mixture into the creamed butter bowl. Then add the dry ingredients and beat until all is well mixed. If it is super stiff add a tablespoon of milk but not too much- as I said it is fine if its a little doughy!
  7. Spoon the batter evenly into the two cake tins. Bake for 20-25 mins in the oven until the sponge spring back when you touch it or the skewer you stick in it comes out clean. When this is cooked place on a cooling rack.
  8. Making the custard- bring the milk and vanilla extract to the boil in a saucepan. Whilst you’re waiting for it to heat up make a paste in a small bowl mixing the egg yolks, sugar and flour. Once the milk in boiling place a little in the paste then add all the paste to the saucepan. Keep on the heat but continuously beat it, but not too hot or it may curdle. Do this for 5 mins until the flour has cooked and the mixture thickens.
  9. Whilst the cake is still cooking tip the custard in a tray, I used one I cook brownies in and cover with cling film to leave it to go cold.
  10. When the cake has fully cooled you can start piecing the cake together! Remix the cold custard. Slice the tops of the cakes slightly to flatten them and smooth them out. Spread the custard on a sponge and sandwich the two sponges together.  Put this in the fridge whilst making the ganache.
  11. For the ganache- heat up the double cream in a saucepan until it is about to boil. Break up the chocolate in a bowl and pour the hot double cream over it and mix until it is all melted.
  12. Place your cake back on the wire rack and put a baking tray underneath- this is going to catch your chocolate! Pour the ganache straight onto the cake and leave it to pour over and the excess will fall into the tray. Repeat until the cake is full covevered. Transfer the cake onto a plate and put in the fridge for the ganache to set.
  13. Decorate your cake when cooled. I put chocolate shavings on mine so used a peeler on the chocolate to do this, then sifted some edible gold glitter I had.


Happy Birthday Mum, I hope you like it!
Love you and thank you for everything you have done and still do for me.







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