Peel the avocado and cut the flesh into large cubes. Zest and juice the lime.
Mix the avocado with the lime zest and juice, olive oil, salt, piment d'Espelette. Whisk the milk into the avocado, incorporating air to give a light and airy texture.
Beat the egg and mix with the cold water. Gradually add the flour, mixing well. Coat the prawns in the tempura batter and then fry for 1 minute.
Serve the prawns with the avocado mousse.
«Add the lime juice a little at a time to ensure that the avocado mousse is not too sour!»