Ingredients:

• 1 kg oxtail
  1 1/2 liter water
  4 dry onions
  4 carrots
  2 celery stalks
  2 medium sized potatoes
  2 leeks
  olive oil
  salt & pepper
• For the garnish
  ½ cup yogurt
  2 Tbs olive oil
  gratings and juice of 1 lemon
  freshly ground pepper 
   
     
  Instructions:  
  Finely chop the vegetables and sauté them in olive oil. Add the meat and the water, salt and pepper and let it boil over medium heat for about 1 hour or a bit longer until the meat is tender.
• Remove the meat and mash the vegetables. Remove the bones from the tail pieces and add the meat in the soup.
• Serve the soup and garnish the plates with the yogurt mixture, which is prepared as follows: Mix in the yogurt with the olive oil, the juice and the lemon gratings and the freshly ground pepper. You can even add finely chopped tender celery leaves.