Put the iced cake in the fridge while you make the strawberry ganache. Put the white chocolate in a small heatproof bowl and set aside. Put the cream and strawberries in a saucepan over a medium heat and cook, stirring all the time, until the strawberries have broken down and the cream starts to simmer. Quickly pour the hot cream mixture over the white chocolate and leave it, without stirring, for 1 min, then add the food colouring and mix until smooth.