All the ingredients, including the eggs, should be brought to room temperature before use.
Cream the butter first, to soften, in the large bowl of an electric mixer or a large glass bowl. Beat in the sugar.
Beat the butter and sugar together until light and creamy. Use an electric mixer, electric hand beaters or a wooden spoon.
Add any flavourings and gradually beat in the eggs, one at a time, in about six additions. Beat well between each addition to prevent curdling. If the mixture does curdle, add a little flour.