Preheat the oven to 360 F (180 C). Line a 12 hole muffin tin with patty cases. In a large mixing bowl, sift the flour, cocoa powder, baking soda, baking powder and then add the sugars – give it a stir. Place the butter in a microwave safe mixing bowl and pop into the microwave for 10 seconds or so at a time, until it is just melted. Give it a stir with a fork to eliminate any lumps. Then add the eggs and vanilla to the butter, along with the buttermilk and whisk together until smooth. Then add the wet butter mixture into the dry mixture and fold until just combined. Spoon the mixture into the prepared patty cases and pop into the oven. Bake for 18-20 minutes before setting the cakes onto a wire rack to cool completely.

To make the marshmallow filling, add a few inches of water to a medium saucepan and place on a medium heat. In a small heatproof bowl, add your eggs whites, caster sugar and cream of tartar. Whisk together. Then pop the bowl over the saucepan, ensuring the bottom of the bowl does not touch the water. As the egg whites heat, whisk gently by hand the entire time. You’ll want to heat the egg white mixture to 120 F (50 C) which you can test by sticking a candy thermometer into the mixture or go by feel (the mixture should be hot to the touch) – should be around 5-6 minutes or so. The mixture should become smooth and the sugar should be dissolved. Remove the bowl from the saucepan and place in the base of a stand mixer (or simply use a hand beater) and beat on medium speed for approximately 7 minutes until the mixture is fluffy, white and voluminous. Add the vanilla and beat for 30 seconds or so.

Use a knife to cut out a hole in the middle of each cupcake – but keep these cake cores. Fill a piping bag fitted with a large round tip with the marshmallow fluff frosting and pipe into the middle of each cupcakes – be careful not to overfill them. Then cut the tops off your cake cores and press on top of the marshmallow filling so the cupcake has a closed top once again. Continue with all 12 cupcakes.

Then it’s time to make the chocolate ganache. Roughly chop your chocolate and place into a small bowl. Then gently heat your cream over a low heat on the stove until it becomes warm to the touch but do not boil. Pour the warm cream over the chocolate and leave for approximately 1-2 minutes. Then gently whisk the mixture until combined and smooth. Pop the chocolate ganache into the fridge to cool and thicken slightly for about 20 minutes or so. It’s really up to you how thick or thin your would like the ganache. You can refrigerate it for longer if you want it thicker. Give it a stir and then drizzle over the top of each cupcake. I like to remove the cupcake liners here so the chocolate ganache can drip down the sides.

Finally, it’s time to make the buttercream for the swirls. In a small bowl, add your butter (ensuring it is nice and soft) and give it a good stir with a spoon. Then add half of your powdered or icing sugar, milk and vanilla and stir together. Once it is smooth, add the rest of the powdered or icing sugar. Then transfer this mixture to a piping bag fitted with a small round tip and pipe the swirls on top. Just make sure the ganache has set slightly so the two frostings don’t run together. Enjoy!