yield
Makes 4 to 6 servings
Ingredients
For meat and vegetables
2 3/4 pound veal breast (bone in)
1 pound boneless veal shoulder, trimmed and cut into 2-inch pieces
2 1/2 quarts water
6 fresh parsley sprigs
2 fresh thyme sprigs
1 bay leaf (not California)
4 black peppercorns
2 onions, halved
4 carrots, quartered crosswise
1 leek (white and pale green parts only), halved lengthwise and cut crosswise into 1/2-inch pieces
2 tablespoons unsalted butter
1/2 pounds mushrooms, quartered

For sauce
3 tablespoons unsalted butter
3 tablespoons all-purpose flour
2 large egg yolks
2 tablespoons crème fraîche
1 1/2 tablespoons fresh lemon juice

Preparation

 Stew meat and vegetables:
1. Cut meat away from veal breastbone, reserving bone, and cut meat into 2-inch pieces. 
2. Bring veal breast and shoulder, veal bone, and water to a boil over moderate heat in a 7- to 8-quart heavy pot, skimming froth. While water is heating, wrap parsley, thyme, bay leaf, and peppercorns in a small square of cheesecloth and tie into a bundle to make a bouquet. Add bouquet garni and onions to pot and simmer, uncovered, until veal is tender, 1 1/4 to 1 1/2 hours. 
3. Preheat oven to 300°F. 
4. Transfer veal with a slotted spoon to a heatproof serving dish and keep warm in oven, covered with foil. 
5. Discard veal bone, onions, and bouquet garni, then pour stock through a fine sieve into a large bowl. Return stock to cleaned pot, add carrots and leek, and simmer until tender, 10 to 12 minutes. Transfer vegetables to serving dish. Boil stock until reduced to about 2 1/2 cups, about 10 minutes. 
6. While stock is reducing, heat butter in a 10-inch heavy skillet over moderate heat until foam subsides, then cook mushrooms, stirring, until just tender, 6 to 8 minutes. Transfer to serving dish and season veal and vegetables with salt and pepper. Keep warm in oven. 

Make sauce:
1. Melt butter in a 2- to 3-quart heavy saucepan over moderately low heat, then stir in flour. Cook roux, stirring, 3 minutes (do not let brown). Whisk in reduced stock and simmer, uncovered, whisking occasionally, 15 minutes. Whisk together yolks and crème fraîche in a small bowl, then whisk in 1 cup sauce. Whisk yolk mixture into remaining sauce with lemon juice, then cook over moderately low heat (do not let boil), stirring constantly, until it reaches 160°F on an instant-read thermometer and coats back of a wooden spoon.
2. Season sauce with salt and pepper and pour over veal and vegetables.

http://www.epicurious.com/recipes/food/views/Veal-Stew-Blanquette-de-Veau-104763