My Mum always made these, now I make them. It's from a flour company called Be-ro.

Rich Biscuits

225g SR Flour (use a biscuit/cake flour if you can)
100 caster sugar
100 butter or margerine
1/2 lemon, grated rind and juice
1 medium egg beaten

Heat oven 180 deg, grease two baking trays or line with baking paper
Mix flour and sugar, rub in butter or margerine
Add lemon rind, juice and add sufficient egg to make a stiff dough
Roll out thinly and cut (using whatever shapes you like)
Bake for 15mins, makes around 24.