Kakavia (fish soup) from St. Galini, Crete

Take a large pot and line its bottom with a layer of potatoes. A layer of fish over those and then potatoes on top of that. 

Place the onion on one side. 

Pour in the cup of oil and that with the lemon. If the liquids don't cover the ingredients add a bit of water. (For a stronger taste, repeat the doses of lemon juice and oil until the ingredients are covered). 

Place the pot over heat. On top of the last layer place a plate so that the ingredients don't move when it starts to boil. Cook over strong heat for quite a bit of time. The lemon and oil will turn into a nice cream and the soup will be all white. 

Serve the fish, potatoes and stock in plates.