1-Melt butter over medium heat, add onions and saute for a minute or two, add garlic. Put in the chopped lettuce and potatoes, add dried coriander, salt and pepper. Mix well and saute for 2 minutes, then add water or stock to cover the ingredients in the pot.
-Simmer for 20-30 minutes until potatoes are cooked.
-Turn off heat, use and immersion blender or a regular blender and process all the ingredients until you get the consistency of a soup (not too runny, not too thick).
-Adjust seasoning, serve warm.