Divide and scoop out the avocados. Put them in a blender.
Peal the grapefruit, and squeeze a little bite of the juice on the avocado.
Blend the avocado and grapefruit juice until it is very smooth.
Whip the cream in a bowl.
Add the avocado in the cream and stir it together gently.
Put the grape fruit in the blender, and mix gently.
Pour away the juice from the grapefruit.
Put the grape fruit flesh in the bottom of the serving bowls.
Put the avocado mousse on top of the grape fruit.
Put the mousse in the fridge until it is time to serve.