Chicken with Truffles and Champagne Sauce

Name: Chicken with Truffles and Champagne Sauce
Ingredients: 1/2 cup all purpose flour; 1 3 3/4-pound chicken, cut into 8 pieces; 1 1/2 tablespoons unsalted butter; 2 tablespoons extra-virgin olive oil; 1/2 cup minced shallots; 2 cups Champagne or sparkling white wine; 1 bay leaf; 8 ounces green beans, cut in half crosswise, then lengthwise; 2 cups matchstick-size pieces celery root (about 8 ounces); 1 1/4 cups matchstick-size pieces carrots (from 1 large); 3 large egg yolks; 1 small black truffle, cut into matchstick-size pieces (optional)