Sour Soup with Lettuce

Ingredients

• / 2 l water
  2 quarts
• Boston lettuces with firm cores
  2 unit
• carrot
  1 unit
• parsley root
  1 unit
• big onion
  1 unit
• garlic clove (optional)
  1 unit
• flour
  1 tablespoon
• yolks
  2 unit
• sour cream
  2 tablespoons
• – 3 tablespoons vinegar
  2 unit
• chopped parsley
  1 unit
• salt
  1 unit