Add the currants and lemon zest and bring the biscuit mix together into a ball. You might need your hands for this bit! Dust a surface with flour and roll the biscuit mix out until about 1/2 a centimetre thick. Cut the biscuits out with a fluted biscuit cutter (Nana says they must not be plain edged!) and put each one onto a greased baking tray.
Brush the top of each biscuit with the egg white and sprinkle with caster sugar. Bake in a preheated oven at 180C for 10-12 minutes until golden brown. When done, put on a wire rack to cool. They won't be around for long!
All That I'm Eating