Shelagh made this for one of our Discovery Days here at GC and it's really delicious - if you have preserved lemons even better!
Green lentils (soak beforehand if possible to reduce cooking time)
Boil green lentils till half cooked - about 20 mins if not pre-soaked.
Sweat leeks in olive oil till soft.
Add lentils and stock. Cook till lentils are fully soft.
Blend about half the soup with grated lemon zest, parsley and lemon juice to taste (or use preserved lemons if you have them).
Season if needed.