Preheat your oven to 200°C (gas mark 6, 180°F) and line a baking tray with parchment paper.
In a large mixing bowl, cream together butter and sugar until light and fluffy.
100 g Butter, 75 g Caster Sugar
Add an egg yolk and mix until combined.
1 Egg Yolk
Add the flour, currants and grated lemon zest into the bowl and mix together until evenly combined. Use your hands to help bring the dough together.
200 g Plain Flour, 50 g Currants, 1 Lemon Zest
Lightly flour your work surface and knead the dough until it forms into a ball. Then, roll out the dough until it reaches a 5mm (1/4 inch) thickness.
Use a fluted (or round) 6cm cookie cutter to cut out the biscuits and place it onto your baking tray lined with parchment paper. Repeat this step until you have used up all the dough.
Bake the Shrewsbury biscuits in the oven for 8 to 10 minutes or until it starts to brown. Leave the biscuits to cool down before transferring to a plate or cooling rack.