Moreish Lemon Biscuits

Name: Moreish Lemon Biscuits
Prep time: 8 min
Cook time: 17 min
Total time: 25 min
Cuisine: British
Ingredients: 150 g butter; 250 g caster sugar; 50 g light brown sugar; 1 pinch fine sea salt; 2 pieces unwaxed lemons (zest and juice); 1 medium egg; 250 g plain flour (all-purpose); 30 g cornflour (cornstarch); 1 tsp baking powder; 1/2 tsp bicarbonate of soda / baking soda; 1 tsp citric acid (optional)