250g butter, chopped
2 teaspoons vanilla essence
2 cups (440g) castor sugar
2 cups (300g) self-raising flour
1/3 (40g) custard powder
1 cup (250ml) milk
Grease deep 23cm square cake pan, line base and sides with baking paper.
Combine all ingredients in large bowl of electric mixer, beat on low speed until ingredients are combined. Then, beat on medium speed until mixture is smooth and changed in colour. Spread into prepared pan.
Bake at 160ºC (325ºF) about 1 ¼ hour. Stand 5 minutes before turning onto wire rack to cool.
Dust cold cake with sifted icing sugar, if desired.
Source: The Australian Women's Weekly Quick-Mix Cakes and Deliciously Easy Muffins