1 lb (500 gr) mushrooms
8-10 green onions
2 garlic cloves
1/2 stick/55g butter
2-3 Tbsp. dry white vermouth
5 cups/1 liter mild chicken stock (or boil chicken wings or a chicken leg/thigh)
3 egg yolks
1 1/4 c heavy cream
2 tsp. chopped parsley
2 1/2 tsp.salt
1/4 tsp. pepper
Chop onion and garlic and melt butter in a large pan. Chop mushrooms in food processor. Sweat the onions and garlic in the butter for ~2 mins. Add the mushrooms to the onions and stir them around for a few minutes, and then add the vermouth.
In another pan, bring the chicken stock to the boil and then pour it onto the vegetables. Simmer for 15 minutes.
Beat the egg yolks with the cream, add a few ladles of the soup, then pour the mixture into the pan. Add the parsley and seasoning and heat very slowly, stirring all the time. Do not allow the soup to boil or it will curdle. When the mushrooms are suspended in the soup, serve immediately.
NOTE: It helps if you prepare the stock the day before you do the soup. When you refrigerate the broth, the fat congeals and you can remove it. Boil the chicken bones for about 50-60 minutes. No need to put carrots, onions, etc. Make sure that you have 5 cups after boiling.