Roughly chop the white chocolate, then melt with the condensed milk in a heavy-based pan over a very low heat for about 10 minutes.
Once it’s melted and well mixed, beat in the icing sugar with a whisk or electric beaters, then beat in the desiccated coconut and the coconut flavouring. Carefully taste the mixture, then add a more coconut or flavouring if needed.
Pour the mixture into a lined 20cm x 20cm tin and spread out evenly with a spatula.
Put it into the fridge to set for 3 to 4 hours before removing from the tin and cutting into 2 to 3cm squares.