preheat oven to 180·c

grease pan and line with baking paper

beat butter, castor sugar and vanilla essence together until creamy

sift both flours into the butter mixture

stir in the flour until a soft dough forms

press into a lined pan

bake for 15 to 20 minutes until golden. set aside to cool

whisk the eggs, lemon zest, flour and sugar together until smooth

add lemon juice and whisk to combine

pour over the base and bake for 15 minutes or until set

cool completely in the pan

dust with icing sugar and cut into pieces

for a delicious crunch, mix whipped egg whites with shredded coconut and top the bars with this mixture. bake for an additional 15 minutes until brown