Rinse meat and pat dry. Put veal bones in a large pot, add wine and enough water to cover bones. Season with salt and boil. Skim off foam.
Peel onion and press cloves into it. Peel carrots and cut in half. Peel garlic. Add vegetables, herbs and peppercorns to pot. Simmer over low heat for about 1 1/2-2 hours.
Melt half the butter in a saucepan. Whisk in flour and deglaze with some of the broth. Remove from heat and let cool.
Heat 1 tablespoon butter in another saucepan. Cook peeled, small onions. Deglaze with some broth and let simmer.
Remove veal from pot and drain. Cut into large cubes. Heat remaining butter in a pan and brown veal. Remove bones from stock and discard.
Strain broth through a sieve. Whisk butter-flour mixture into broth. Let broth simmer until thickened. Combine egg yolk, crème fraîche and 2-3 tablespoons of broth. Pour mixture into broth and mix well.
Put veal and onions in a Dutch oven. Pour sauce over top. Cook over low heat, do not boil. Season with salt, lemon juice and pepper. Garnish with parsley and serve, as desired, with white bread.