A thick, hearty, main-dish soup to take the chill off any winter’s day. Serve hot with fresh yeast rolls sliced and browned in butter. Although it is still flavorful reheated the next day, it begins to thicken even more as the potatoes cook down.
Saute bacon in a deep saucepan for 5 minutes, or until nearly crisp. Add leeks and onion, and saute for another 5 minutes. Stir in flour. Add broth slowly, stirring constantly. Add potatoes and simmer for 1 hour. Combine egg yolks and sour cream, and stir into soup. Simmer for 10 minutes, stirring constantly. Add parsley and chervil.