3 tbs lemon juice
Butter and line a 20 x 30 slice tin with baking paper, high enough to help you pull the slice out of the tin when set.
Crush the shortbread in a food processor until they become fine crumbs.
Place the crushed biscuits, coconut, lemon rind and condensed milk into a large bowl. Add the melted butter and stir well to combine.
Press the ingredients into the prepared tray as smoothly and as flat as you can.
To make icing, sift the icing sugar and stir through the melted butter. Add the lemon juice 1 tbs at a time until you have a smooth consistency. Spread over the slice and refrigerate until firm.