How to make
Chop or grind the onion, leeks and celery in a blender. Stew them with a little salt in olive oil heated over moderate heat for 7 minutes.
Add the finely chopped mushrooms, another pinch of salt and continue cooking for another 6-7 minutes, by adding the tomato puree with the spoonful of sugar, halfway of the cooking time.
Add water as thick as you want your soup to be. Season with the thyme, parsley and vegetable seasoning and boil it covered for 12-15 minutes, by increasing the heat a little.
Finally, add the noodles and boil for 3-4 minutes or as long as the instructions on the package say.
Remove it from the heat and as soon as the temperature drops a little (5-6 minutes), add the beaten egg yolks, yogurt and black pepper.
Serve the mushroom soup while it's hot.
Enjoy your meal!