1.Combine milk, water and sugar in a saucepan. Stir over a low heat, until sugar is dissolved; do not boil. Add gelatine to extra water. Add gelatine mixture to sugar mixture; stir to dissolve. Cool to lukewarm.
2.Beat butter and vanilla, until white and fluffy. Gradually add cooled sugar mixture. Using an electric mixer, beat 10-15 minutes, until light and fluffy and quite cold. Serve.
Mixture will thicken on standing. Not suitable to freeze or microwave.Note