• Preheat the oven to 180'C (170'C fan) / Gas 4. Fill either one 18-hole or two 12-hole muffin tins with fairy cake cases. (This recipe makes around 18 fairy cakes so I tend to use two 12-hole tins).
• Add the butter, sugar and vanilla extract to a large mixing bowl and beat with an electric whisk until pale and creamy. (TIP: If the butter is hard, zap it in the microwave for 10-15 seconds before adding it to the mixing bowl to make it easier!)
• Crack the eggs into the mixing bowl and beat again for 30 seconds to combine. Scrape down the sides of the bowl using a spatula.
• Sift in the self-raising gluten free flour and xantham gum and then beat together with the electric whisk until everything is fully combined. Add the milk 1 tbsp at a time, mixing in between. You want a fairly thick batter which drops from the spoon easily, so you may need either 2 or 3 tbsp of milk.
• Spoon the mixture evenly between the cake cases and then place in the centre of an oven and bake for 20 minutes. The cupcakes are done when they are well-risen, golden on top, and a skewer inserted in the middle comes out clean.
• Once cooked, remove from the oven and place on a cooling rack. Cool in the tray for 10 minutes before removing the cakes from the tray to cool completely before icing.

To decorate

• Add the icing sugar to a bowl and then add the water one-spoon-at-a-time, mixing in between. Keep mixing with a spoon until it forms a thick paste. You want the icing to be a little runny, but thick enough that it doesn't go transparent when it's put on the cakes.
• Spread the icing onto the cakes, splitting the amount evenly between them, and then finish by sprinkling with sprinkles before the icing sets. Leave to set for 15 mins before eating.