Biscuits with no nuts

These are melt in the mouth 

225g (8oz) soft butter or margarine
140g (5oz) caster sugar
280g (10oz) plain flour
1 egg yolk
pinch of salt
2tsp vanilla extract, or the juice and rind of 1 lemon

Optional extras - Add about 50g of extra ingredients
chopped mixed peel

Chopped mixed nuts
finely chopped dried fruit
chocolate chips or grated chocolate

Cream the butter until light and fluffy.   

Add sugar and beat together until they're light and fluffy.    

Add the egg yolk and mix well. 

Then sift in the flour and salt, and vanilla extract or lemon.   

Mix the flour and your added extras until it all comes together to form a sticky cookie dough.   

Put the dough onto a floured work surface, and work into a thick sausage shape. 

Wrap the cookie dough in clingfilm and leave in the fridge for at least 1 hour. 

While it's in there, preheat the oven to 190C. 

Take the sausage of cookie dough out of the freezer: it should be firmer and easier to cut. 

Use a sharp knife to slice it, as thick as you like, and put the cookie slices onto a baking sheet, spaced quite far apart. 

If you need to bake them in more than one batch, wrap the excess dough and put it back into the fridge so it doesn't go soft.  Bake in the oven for about 15 minutes, then cool on a rack.

Warning: Try not to eat the cookie dough before cooking