Cold avocado soup

Cold avocado soup
Leaves from 6 stalks of lemon basil
Leaves from 2 stalks of mint
Grated zest and juice of 1 organic lemon
300 g ripe avocado (Hass variety)
A litre of cold buttermilk
2 tbsp. olive oil/2 tbsp. rapeseed oil
Cayenne pepper
Coarsely chop approx. 2/3 of the herbs. Halve the avocado, remove the pit and extract the flesh from the skin. Purée in the blender with the buttermilk, lemon zest and 3 tbsp. juice before seasoning with salt and cayenne pepper.
Mince the remaining herbs. To serve, sprinkle the soup with herbs and pepper and drizzle with olive oil.