Wash the potatoes and celeery and cut into small pieces. Set a large saucepan over low heat and – once hot – add the oil, then the celery and potatoes. Fry gently for 10 minutes or until soft and golden. Add the vegetable stock and bring to the boil. Add the frozen spinach and return to boil, then reduce to a simmer, cover and cook for 10 minutes.

Wash the watercress and strip the leaves from the stems. Keep a few for decoration and roughly chop the rest of the leaves. Add the watercress to the saucepan and then simmer for a further 10 minutes.

Purée the soup using a stick blender until smooth. Stir in 100ml cream – keep a bit for decoration – and season with za'atar, nutmeg, salt and pepper. 

Cover the bottom of your frying pan with water and heat over medium heat. Once cooking crack the eggs into the pan. Cook the eggs, covered, for about a minute. Cooking for 1 minute will produce an egg with a runny yolk. If you prefer a more well-done yolk, cook for about 2 minutes. Use a spatula to remove the eggs from the pan.

Reheat the soup and divide between 4 bowls. Add a swirl with the remaining cream. Add the sunny side up to your bowls and some of the leftover watercress. Sprinkle some za'atar over it and serve!