Put the oil in to a frying pan and soften the leek over low heat for 10 minutes, being careful not to brown or burn. It should be quite soft when it's done.
Remove leek from the pan and put aside to cool.
Place leek in a blender or food processor and blend until smooth.
Add the avocado flesh and coconut cream in the blender and blend until smooth.
Add the stock and salt to the blender and blend until everything is thoroughly combined.
When ready to serve, pour the soup from the blender in to a saucepan, heat over low-medium heat, stirring frequently and being careful not to overheat.
At the same time as heating the soup, brown the mushrooms and crisp the proscuitto in a frypan with some oil or other fat.
When the soup has reached the desired heat, check for taste and adjust with salt if necessary.
Serve garnished with mushrooms and proscuitto and with some crusty bread.
Can be stored in the fridge for up to 3 days.