Nutmeg, salt, white pepper Saute onion in butter in heavy skillet until onions become soft and transparent, then add garlic and cook a few minutes more. Stir in the flour and cook for about 3 minutes more--careful not to scorch! Pour the milk in and immediately wisk to blend. Add the herbs and bring to boil stirring to avoid lumps. Simmer for at least 15 minutes. Season to taste with nutmeg, salt, pepper. Before serving, whisk the egg yolks into the cream then whisk the mixture into the soup. You can substitute milk for the cream if you want a lighter soup.
This soup is an excellent base for a wide variety of soups. I like to add fresh herbs and sometimes some cheese to the soup. Chopped ham, turkey, or chicken (leftovers), or any diced begetables can make an even meatier soup. If you add pureed vegetables you might want to reduce the amount of flour to keep the soup from getting too thick.
You can saute chopped vegetables separately and add right after the milk is poured in for wonderful vegetable cream soups. Cabbage and Brussels Sprouts are two that work particularly well.
The original of this recipe is from Francois Kissel who had the Brasserie Pittsbourg in Seattle--an outstanding restaurant!