I use this recipe. Perfect every time:
Suitable for freezing before decorating.
100g/4oz slightly softened butter
50g/2oz caster sugar
175g/6oz plain flour
pinch of salt
a few drops of vanilla essence
Preheat the oven to 180C/350F/Gas 4.
Beat the butter and sugar until thoroughly mixed.
Sift (I never sift) together the flour and salt and mix this into the butter mixture.
Add a few drops of vanilla essence (I don't) to form a fairly stiff dough.
If the dough is too dry add a little water.
Form the dough into a ball using your hands, then roll out thinly on a floured work surface using a rolling pin dusted with flour
Cut into shapes using biscuit cutters.
Arrange on greased or lined baking sheets and bake for about 12 to 15 minutes or until the biscuits are lightly golden.
For the icing:
100g/6oz icing sugar sifted
½tbsp lemon juice or water
put icing sugar in a bowl with enough lemon juice or water to make a good spreading/ piping consistency. Pipe or spread on (I always pipe)