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A recipe for my 29th birthday cake… a chocolate and vanilla fault line cake!

Happy Birthday to me!

Happy 29th birthday to meeeee! Yes that’s right, I am now one year away from being thirty. Let’s just avoid that little fact, and talk about all things cake! This post, is this years birthday cake!! 

I always bake myself a birthday cake as I love baking cakes – but its also a good idea for a celebration cake style recipe for my blog, so I always love to post them onto here and my social media channels. 

Fault line cake

Over the years I have gone down quite the chocolate theme for my birthday cakes – as I am a true chocoholic. I can’t resist them – but this year I thought I would do something I haven’t done on my blog before, and do a fault line cake!

I will say now before anyone asks – there is no video tutorial for this cake. As it was for my birthday and I baked this yesterday, I didn’t have the time to video it – sorry… hopefully will do a tutorial video for a fault line cake at some point!


I decided to do a chocolate cake for the base cake of the recipe as I still wanted a little chocolate in my birthday cake this year – but used a vanilla buttercream frosting for the decoration. I love the combination of chocolate and vanilla and this is a good method of achieving it. 

I used a four layer cake – baking into two of these cake tins. A slightly lower baking time means it bakes flat, and it stays moist! It’s the charm of baking a slightly deeper cake too. Although, don’t take them out too early, as the cakes will really sink if you do! 


When decorating a cake, I do find it easier when the sponge is frozen – some people may disagree with this, but honestly – it’s so good. I bake the cakes, cool them, and then half them ready. Double wrap in cling film and then foil and freeze until required! 

I used a pale pink/peach colour buttercream as the base – but you can obviously use whatever colour you prefer. I filled the cake with this buttercream, used it for the crumb coat, and then also the decoration! 

Fault line

When doing the ‘fault line’ part – it can get a little messy if you use sprinkles like I did! I spread a little of the buttercream around the middle section of the cake using a small angled spatula, and pressed some sprinkles carefully into this buttercream. You don’t need much buttercream, just enough to use as ‘glue’. 

Some sprinkles will inevitably fall off, so this is how it can get messy – but it’s fun! You can use any colour or type, but you don’t want the feature part of the cake to stick out too much, as the rest of the buttercream will have to be wider to create the look of the bake. 


Once I have pressed the sprinkles into the cake I chilled the cake in the fridge to set the sprinkles. I then used a piping bag to pipe buttercream around the cake bottom and top so that it was thick. I then used my large metal scraper to smooth the buttercream around the edge – this creates the look of the bake. 

Don’t worry if you cover some of the sprinkles, or if it looks a little rugged – this is good! It creates the jagged edge that is perfect for a fault line cake. Once the buttercream has been smoothed around the edges and top of the cake, I chill it again. 

Extra touches

I used a little rose gold food paint to paint around the edges of the lines, to make it more of a feature – and then also did some paint splats as I got a little bored and carried away… sorry to the tiles behind the cake that became a little rose gold too haha! 

I used the leftover buttercream to pipe tall swirls of buttercream on the top – and sprinkle on more of the sprinkles, and some large pearl sprinkles for an extra touch! This is of course, optional. 

All of this is just what I happened to do for this years birthday cake – hopefully it can give you guys some inspiration for if you want to make your own fault line cake! Enjoy! X

My 29th Birthday Cake!

A recipe for my 29th birthday cake… a chocolate and vanilla fault line cake!
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Category: Cake
Type: Drip Cake
Keyword: Chocolate
Prep Time: 1 hour
Cook Time: 1 hour
Decorating Time: 3 hours
Total Time: 5 hours
Servings: 20 Slices
Author: Jane's Patisserie


8" Chocolate Cake

  • 500 g unsalted butter/baking spread
  • 500 g light brown sugar
  • 400 g self raising flour
  • 100 g cocoa powder
  • 10 medium eggs


  • 600 g unsalted butter (not stork) (room temp)
  • 1200 g icing sugar
  • 1 tsp vanilla extract
  • 1 tsp pink food colouring


  • Rose gold paint
  • 100 g sprinkles
  • Feature sprinkles


For the 8" Chocolate Cake!

  • Preheat your oven to 170ºC/150ºC Fan, and line two 8"/20cm deep cake tins with parchment paper.
  • Add the butter and sugar to a bowl, and beat until light and fluffy.
  • Add in the flour, cocoa powder and eggs and beat again until a lovely smooth cake mixture is formed.
  • Split evenly between the two tins and bake in the oven for 50-60 minutes (or until a skewer comes out clean!)
  • Once baked, leave to cool in the tin for 10 minutes, and then leave to cool fully on a wire rack.


  • Beat the unsalted butter on its own for a while in your mixer until its smooth and supple.
  • Add in your icing sugar a little at a time and beat fully until its light and fluffy and add the vanilla extract and food colouring!
  • (If the mixture is really stiff, add in 1-2tbsp of boiling water and beat fully to smooth out)


  • Level the cakes off if necessary. Split the two cakes into two so you have four layers in total
  • Add your first cake to a cake board or flat serving plate and secure with a small amount of buttercream.
  • Spread some buttercream onto the first layer, add the second sponge. Repeat until you reach the top layer of cake.
  • Spread some buttercream around the sides to fill in the gaps and create a crumb coat. Refrigerate the cake for at least 30 minutes.
  • Once refrigerated, using an angled spatula, spread a thin layer of buttercream around the middle section of the cake and carefully press in the sprinkles with the palm of your hand and then smooth around using a large metal scraper.
  • Chill the cake again for another 30 minutes.
  • Once chilled, pipe or spread some more buttercream in a thicker layer around the top section and bottom section of the cake and then smooth around using a large metal scraper. Smooth some buttercream on to the top of the cake as well.
  • Refrigerate the cake for another 30 minutes.
  • I then used some rose gold paint to paint around the edges of the fault line, and then also flicked some onto the other sections of the cake.
  • Pipe some swirls of the leftover buttercream on top using a medium 2D closed star piping tip and decorate with the sprinkles.


Find my other recipes on my Recipes Page!

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J x

© Jane’s Patisserie. All images & content are copyright protected. Do not use my images without prior permission. If you want to republish this recipe, please re-write the recipe in your own words and credit me, or link back to this post for the recipe.


  1. Kelly on April 17, 2023 at 9:50 am

    How much would you increase your cake mix by to make a 10inch cake?

  2. Michelle dunn on August 12, 2022 at 6:53 pm

    Hi Jane which pink food colouring did you use for this cake?

    • Jane's Patisserie on August 16, 2022 at 9:37 am

      Hiya! The pink colouring is linked in the notes. Hope this helps! x

  3. Angela on March 18, 2022 at 4:01 pm

    5 stars
    Made my daughters cake following your easy vanilla cake recipe (made 4 layers) then followed this design. She absolutely loved it! Thank you.

  4. Helen on October 26, 2021 at 10:13 am

    5 stars
    Hi Jane 🙂
    Just to let you know a company on Facebook are using your pictures and passing them off as their own bakes.
    Cumbrian Cheesecake Vintage Tea Rooms – post dated 18/10/21.
    I commented they were committing copyright infringement but they have just removed the comments and left the pictures up.
    The pictures are clearly yours and watermarked.
    Thank you for all of your wonderful recipes 🙂
    Helen x

    • Jane's Patisserie on October 26, 2021 at 12:59 pm

      Ahh thank you so much! I found the images and I believe they have been removed now – I appreciate the help! x

  5. Pauline Bone on October 23, 2021 at 5:56 pm

    Hi Jane
    Not directly connected to this recipe but was just wondering how you go about this Natashas Law thing. I’m a self taught home Baker but occasionally my traybake bites I sell at little local Fayres. I’m so confused how much detail has to go into allergen labels etc, would be forever grateful for any tips or advice you could give me please. It’s thanks to you and your amazing recipes that a year later I’m trying different things every week. Thank you for your inspiration 🥰

    • Jane's Patisserie on October 25, 2021 at 10:49 am

      Hiya! Please contact your local council – if selling bakes then you need to be registered and they will have all of the information for you! Hope this helps! Team Jane x

  6. Gabriela on October 22, 2021 at 2:52 am

    Happy Birthday <:)

  7. Cherry on October 20, 2021 at 8:01 pm

    You’ll always be young if you eat your wonderful cakes!
    Belated Birthday wishes 💕

  8. Julie+Jankowski on October 20, 2021 at 4:09 pm

    5 stars
    This looks amazing Jane.Happy Birthday xx

  9. Ann Sanders on October 20, 2021 at 12:59 pm

    5 stars
    Happy birthday lovely lady, your special cake is amazing . You deserve the most brilliant day ever.xxxxxx🥳🍷🎊🎈💝🤚🤞

  10. Claire Cox on October 20, 2021 at 12:54 pm

    5 stars
    Wow Jane looks amazing. Definitely inspired me to try something in the future. When you say to freeze for decorating. How long in advance of decorating could you make and freeze ahead of time without it going too dry?

    • Abigail on February 1, 2022 at 5:12 pm

      How do you store this until you are eating it?

    • Jane's Patisserie on February 3, 2022 at 1:24 pm

      Hiya! You can store this in the fridge prior to slicing, but after slicing, store it at room temperature! Hope this helps! x

  11. Wendy beattie on October 20, 2021 at 10:49 am

    Love your cakes I bought your book which is my pride and joy and sitting open on my cast iron book rest in my kitchen.I went through the past two and a half years with a very deep depression after my son took his life.Then I discovered your cakes recipes and I got stuck into making your wonderful cakes and has been the best therapy for me.Then I bought your book a couple of weeks ago it’s fantastic.Much thanks.

  12. Janet on October 20, 2021 at 10:00 am

    That cake is truly amazing! The skill involved…absolutely wow. Happy Birthday!

  13. Nicoletta on October 20, 2021 at 9:08 am

    Happy Birthday !!Looks fantastic and tasty

  14. James Bennett on October 20, 2021 at 8:21 am

    Great timing on this post Jane- I turn 30 next week, and an earthquake/fault line themed cake seems apropos. I reccomend just staying 29.

    Four layers of chocolate will be exactly what I need to turn my inevitable frown upside down

    You may be happy to learn that at the place you worked before the blog took off, we still all talk about when you used to bring stuff in, and on our internal company blog, people from other branches and head office are always talking about having used your recipes.

  15. Stacy Morrison on October 20, 2021 at 8:17 am

    Looks amazing!! Happy Birthday 🎂 🥳 🎉 xxx

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