Preheat oven to 180C/350F and line a 12 hole cupcake tin (You may have enough batter to make 14, I just put 2 extra liners on the tray and didn't worry that they weren't perfect cupcake shapes!!)

Place the margarine/butter and sugar into a large bowl, or the bowl of your stand mixer and beat until light and fluffy, about 2 minutes on medium-high speed.

Add in the eggs and vanilla extract and mix until well incorporated, about 1 minute on med-high speed.

Place the cocoa powder, plain flour, baking powder and salt, if using, into a medium sized bowl and stir until combined and there are no lumps of cocoa powder.

Tip the flour mix into your egg mixture and add in the buttermilk. Mix until well incorporated and smooth, 45 seconds-1 minute on med-high speed.

Place the bicarbonate of soda into a small glass and add in the vinegar, stir until it stops fizzing.

Tip into your cake mixture and mix until well combined.

Add in your pink food colouring, a little at a time, mixing in-between additions until you have the desired shade of pink. Be aware that when they bake the colour could become kind of brown, my cake batter was BRIGHT pink!

Divide the batter between your cupcake liners, fill each one 3/4 full.

Place in the oven for 18-22 minutes until risen, springy to the touch and an inserted skewer into the centre comes out clean.

Transfer cupcakes to a wire rack almost immediately, yes they're hot, but this stops the liners peeling away from the cupcakes.

Leave to cool completely, before making the frosting: Place the chocolate chips and butter into a heatproof bowl and place in the microwave, in 20 second increments, stirring in between, until melted and smooth. Leave to cool for 25 minutes.

Once cooled, pour into a large bowl/the bowl of your stand mixer and add in the vanilla. Mix briefly. Add in your sifted icing sugar and mix on low until it starts to combine (to avoid a huge icing dust cloud!) and then turn the speed up to medium and mix until smooth and fluffy.

If frosting is too thick, add milk 1/2tbsp at a time until you have a soft, creamy consistency.

Spoon frosting onto each cupcake and smooth with the back of a spoon/small spatula. TOP TIP: Dip the spoon/spatula into warm water before smoothing over the cupcake, this ensures a smooth finish and makes it easier to work with.

Once all cupcakes are frosted, decorate with marshmallows (I used heart shaped) and add any sprinkles you want!

Cupcakes will keep in an airtight container, at room temperature for 4 days.