125g good-quality unsalted butter, at room temperature
1 teaspoon natural vanilla extract
185g (1 1/3 cups) icing sugar, sifted
2 tablespoons milk, at room temperature
1. Beat the butter in a small bowl with electric beaters until pale and fluffy.
2. Continue beating and gradually add the vanilla extract and half the icing sugar.
3. Gradually add the milk and the remaining sugar and beat until smooth.