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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 ghostbusters 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. 

Food colouring and cupcakes cases

I will admit early on in these slime cupcakes, 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 are using good quality colouring like I recommend then you don’t use much to get good results, so it’s perfect! You can see from my rainbow cake how using good quality food colouring really pays off!

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! 

Black sponge

To make a black sponge for these slime cupcakes, 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 slime cupcakes 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.

The amount of people that look at these and think I have put peas on my cupcakes – they are sprinkles I promise! I love the stick to a theme as always and I think they match the bake perfectly. I hope you love this recipe for slime cupcakes! 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
  • 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/160ºC fan 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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J x

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  1. Helen Little on October 20, 2023 at 1:37 pm

    These are such fun Halloween treats! I’m sure my toddler will help making these – and eating them too. The drizzle looks so perfect.

  2. Claire on October 4, 2022 at 2:34 pm

    Hi Jane,
    The link to the green food colouring isn’t working – could you please tell me which brand and colour you used?
    Many thanks!
    Love, love, LOVE all your recipes & books!

    • Jane's Patisserie on October 6, 2022 at 3:09 pm

      Hiya! it is linked in the recipe notes. Hope this helps & thank you! x

  3. 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

  4. 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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