Preheat oven to 190°C. Sift the dry ingredients together into a bowl.
In a separate bowl beat together the butter and two sugars until creamy.
Meanwhile, in another bowl/jug whisk together the milk, eggs and vanilla extract.
Add 1/3 of the wet ingredients into the butter mixture and mix on a slow/medium speed followed by 1/2 of the dry ingredients.
Scrape down your bowl and beat in 1/2 the remaining wet ingredients followed by the rest of the dry ingredients. Once combined pour in the remaining wet ingredients.
Once the mixture is smooth, evenly divide it into the cupcake cases.
Bake in the oven for 18-22 minutes or until a skewer comes out clean.
Once cooled cut a small circle out of the centre of each cupcake and fill with marshmallow fluff. Place lid of cupcake back on top.
For the buttercream sift the icing sugar into a bowl and beat it into the butter. Once sandy pour in the milk to combine.
