- Grease a Square Sandwich Pan. Soak gelatine in half the water. In a saucepan place the sugar, cream of tartar and remaining water. Stir over a low heat until dissolved. Bring to the boil, add gelatine and boil gently for 20 minutes. Add vanilla and enough food colouring to tint mixture a delicate pink. Pour into prepared pan and leave to set. Using a hot knife cut into small squares. Combine cornflour and icing sugar and toss squares in it.