Cupcakes: Preheat the oven to 160 degrees C. Line a 12 hole cupcake tray with cupcake papers.
Lightly beat the eggs, add butter and sugar, then mix until light and fluffy. Add buttermilk, flour and vanilla and stir then beat with an electric mixer for 2 minutes until light and creamy.
Divide the mixture evenly between the cupcake papers. Bake for 18-20 minutes until risen and firm. Then wait for a few minutes to let them cool then transfer to a wire rack. Make sure the cupcakes are completely cool before icing.
Topping: Mix half the icing sugar and butter then add remaining icing sugar, butter and vanilla extract and beat with a spoon until light and fluffy.
To Serve: Add about a tablespoon of topping to the centre of each cake then stick some mini marshmallows into the topping and enjoy!
You don't have to use marshmallows as the topping, you could use eatable flowers, smarties or gummy bears to make it your own!