Cut the passion fruits in half, scoop out the pulp with a spoon and place in a bowl.
Gently whisk the cream in a large bowl and place in the fridge, along with four glasses.
Sieve the icing sugar into a bowl, and set aside.
When you wish to eat, whisk the icing sugar into the cream with the lemon juice and coconut rum.
Fold in the passion fruit pulp and pour the fool into the chilled glasses.
Serve with biscuits of your choice.