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Delicious scaretastic slime cupcakes with a black chocolate sponge, chocolate black buttercream frosting, and a gooey white chocolate slime drizzle and centre! 

When I think of halloween, I think of all things scaretastic, and I am obsessed. One thing I love to watch on tv at halloween though, is the ghost busters films. I just think all the ghosts and slime makes such a good theme, I had to do something. 

Slimer is one of the most hilarious characters in a film that I have ever seen – not scary at all to me, but leaving a gooey disgusting slime on everyone… why not make a bake about that?! All the green. 

I will admit early on in this bake, there is a fair amount of food colouring, and your tongue may look a little weird after baking – but that’s totally fine in my eyes. If you using good quality colouring like I recommend then you don’t use much to get good results, so it’s perfect! 

So for this bake I decided to use black cases, along with a black sponge – to make it all dark and scareilicious. I will try and stop with the puns at some point… but I am unsure I ever will. I am fully in the mode of halloween baking! 

To make a black sponge, you need to use a chocolate base – I use this cocoa powder which is 100% cacao and really dark, so it is a good base for the sponge. I then use this really good quality black food colouring to make sure it gets as dark as possible. 

Sometimes, food colours do not work – this very much includes all brands and types you can buy from supermarkets – I do not recommend using them at all. I use this black food colouring because it is extra strong, and you need a small amount to get the desired effect. 

Baking these into these beautiful black cases makes something heavenly delicious – but also a little weird looking. It is black cake after all! However, using the buttercream frosting and the green slime ganache contrasts so much better against the black colour. 

For the buttercream I use a simple american buttercream frosting to make the decoration – I use unsalted block butter that I have left to become room temperature, and beat this on its own to make it nice and supple. 

I then add in the icing sugar and cocoa powder and beat again for about 5 minutes to really beat the mixture together and make it light fluffy. I use this black food colouring to make the buttercream, and I used a little vanilla extract because I love it. 

The buttercream is relatively simple, but its the ganache that you want to get right – I used a white chocolate ganache as you need it to be white to make sure you get the green – I used this green food colouring. No white chocolate is actually white in colour though, so this is important to remember. 

One of the reasons it is so important to use a strong food colouring is so that you can add as little as possible, but also to make sure that it colours properly – some good colours can seize chocolate, but this brand does not. 

I used a slightly different ratio for this ganache as I wanted it to be slightly runnier than normal – I wanted it to fill the cupcakes slightly for a gooey centre, and to make it easier to pour on top and make the slime drip more naturally. 

I usually use a ratio of 3:1 when it comes to making my white chocolate ganache, but this time I added in a little more cream to make it that bit runnier – I often get questions about what white chocolate I use, and I use this one. It’s my favourite by far! 

I used a 2d closed star piping tip for the piping as always – if you have read my blog for a while, you will realise that it’s by far my favourite piping tip and it creates the most beautiful swirl. I hope you love this recipe! Enjoy! X

Slime Cupcakes!

Delicious scaretastic slime cupcakes with a black chocolate sponge, chocolate black buttercream frosting, and a gooey white chocolate slime drizzle and centre! 
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Category: Cupcakes
Type: Cupcakes
Keyword: Halloween
Prep Time: 40 minutes
Cook Time: 20 minutes
Cooling & Decorating Time: 2 hours
Total Time: 2 hours 50 minutes
Servings: 12 Cupcakes!
Author: Jane's Patisserie



  • 200 g unsalted butter/stork
  • 200 g light brown soft sugar
  • 150 g self raising flour
  • 50 g cocoa powder
  • 4 medium eggs
  • 1 tsp vanilla extract
  • 1 tsp black food colouring


  • 200 g unsalted butter (not stork) (room temperature)
  • 350 g icing sugar
  • 50 g cocoa powder
  • 1 tsp black food colouring


  • 200 g white chocolate
  • 80 ml double cream
  • 1/2 tsp green food colouring
  • sprinkles



  • Preheat the oven to 180ºc/160ºfan and prep 12 black cases.
  • Beat the unsalted butter/stork and light brown soft sugar together until light and fluffy.
  • Add in the self raising flour, cocoa powder, eggs, vanilla extract and black food colouring.
  • Beat the mixture until its thick and lovely.
  • Split the mixture evenly between the 12 cases and bake in the oven for 20-22 minutes.
  • Once baked, leave to cool fully.


  • Beat the room temperatureunsalted butter on its own for a few minutes to loosen it and make it smoother.
  • Add in the icing sugar and cocoa powder and beat again until smooth - I mix for a good few minutes.
  • Then, add in the black food colouring and beat again.


  • Add the white chocolate and double cream to a glass bowl or jug, and microwave until smooth - I do this in 10 second bursts, stirring well each time.
  • Once melted, add in the green food colouring a little at a time and stir in until you reach the desired green.


  • Core out the centre of each cupcake, and fill carefully with some of the green ganache.
  • Pipe the buttercream frosting on top of the cupcake and ganache.
  • Drizzle over the rest of the ganache to create a slimy mess - and add on some green sprinkles if you fancy.



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  1. Mandy on November 2, 2021 at 5:52 am

    5 stars
    Hi, I made these yesterday and they were a bit dry. I checked after 29 mins and they weren’t quite cooked so I gave them another 5 mins until cooked. I’m not sure where I went wrong.

    • Jane's Patisserie on November 2, 2021 at 10:16 am

      Hiya – they are over baked! Cupcakes should take absolutely maximum 25 minutes – might be your oven etc, but they are over baked if they are dry!! x

    • Mandy on November 2, 2021 at 3:35 pm

      Sorry Jane, I made a typo and couldn’t edit. I baked for 20 mins initially and when I skewer tested they weren’t cooked so I gave them another 5 mins. I had the fan oven on 170 as it’s a bit temperamental. Do you still think I overbaked? Maybe I should have just given them an extra 2 mins

    • Jane's Patisserie on November 9, 2021 at 10:35 am

      Hiya! Yes – fan ovens should be at 160 as per the recipe, and please stick to the timings on the recipe to achieve the best bake! Hope this helps x

  2. Sarah on October 27, 2021 at 9:13 am

    Please can I ask why not stork for the unsalted butter?

    I substitute a lot of ingredients due to allergies, I’ve always found that asda cheap “cooking” block works OK or vitalite, so just wondering if there’s something I should be watching out for.

    Emlea vege cream or oatly both substitute well

    • Jane's Patisserie on November 8, 2021 at 10:37 am

      Hiya! In general, for dairy baking, it is important to not use stork for buttercream. But if baking dairy free it is slightly different and can’t be helped! Hope this helps x

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