Preheat and Prepare: First, preheat your oven to 180°C (160°C fan). Line a 12-hole muffin tin with paper cupcake cases.

Cream the Butter and Sugar: In a large bowl, using a stand mixer or an electric hand mixer, beat the 125g of softened butter and 125g of caster sugar together for a good 4-5 minutes. The mixture should become very pale, light, and fluffy. This step incorporates air, which is essential for a light cupcake.

Add Eggs and Vanilla: Beat the 2 large eggs lightly in a separate small bowl. Gradually add the beaten eggs to the creamed butter mixture, a little at a time, beating well after each addition. If it looks like it might curdle, add a tablespoon of your flour. Stir in the 1 tsp of vanilla extract.

Fold in the Flour: Sift the 125g of self-raising flour over the mixture. Using a large metal spoon or a spatula, gently fold the flour into the wet ingredients until it's just combined. What works best for me is a figure-of-eight motion to avoid knocking out the air. Do not overmix!

Loosen the Batter: The batter will be quite stiff. Add 2-3 tablespoons of milk and gently fold it in until the batter has a soft, dropping consistency.

Bake the Cupcakes: Carefully spoon the mixture evenly between the 12 paper cases. Bake on the middle shelf of the preheated oven for 18-20 minutes. They are ready when they are golden-brown and a skewer inserted into the centre comes out clean.

Cool Completely: Leave the cupcakes in the tin for a few minutes before transferring them to a wire rack to cool completely. It is critical they are fully cool before you try to ice them, otherwise the buttercream will melt.

Make the Buttercream: While the cupcakes cool, make the frosting. In a large bowl, beat the 150g of softened butter with an electric mixer for 3-4 minutes until it's very soft and pale.

Add Sugar and Vanilla: Add half of the 300g of sifted icing sugar and beat until smooth. Then add the remaining icing sugar and beat again for at least 5 minutes. The mixture will be very light and almost white. Add the 1 tsp of vanilla bean paste and beat to combine.

Adjust Consistency and Decorate: Add the milk, one tablespoon at a time, beating well until the buttercream reaches a soft, smooth, and pipeable consistency. Transfer the buttercream to a piping bag fitted with a star nozzle and pipe generous swirls onto each completely cooled cupcake.