Grease and line a 18cm x 28cm rectangular slice tin with baking paper.
Crush biscuits and place crumbs into a bowl.
Add desiccated coconut and grated lemon rind. Mix to combine.
Add melted butter, condensed milk and the juice from 1 lemon to the biscuit mixture. Mix thoroughly until well combined.
Press into the prepared tin and place into the fridge.
In a bowl, whisk the icing sugar, room temperature butter and extra lemon juice in a bowl until creamy and 'frosting-like' - if the frosting is too thick to spread, add a little more lemon juice.
Spread the frosting over the slice, sprinkle with the extra coconut and place back into the fridge to firm completely.
Cut into pieces once slice has firmed.
Store in an airtight container in the fridge for up to 1 week.Thermomix Instructions - Click the link in the notes section below for the Thermomix recipe.