Step 1

Combine wine, onion, celery, carrot, garlic, and peppercorns in large pot. Bring to boil over high heat. Reduce heat to medium and simmer 5 minutes. Cool completely; mix in oil. Place chicken pieces in large glass bowl. Pour wine mixture over chicken; stir to coat. Cover and refrigerate at least 1 day and up to 2 days, turning chicken occasionally.

Step 2

Using tongs, transfer chicken pieces from marinade to paper towels to drain; pat dry. Strain marinade; reserve vegetables and liquid separately.

Step 3

Heat oil in heavy large pot (wide enough to hold chicken in single layer) over medium-high heat. Add bacon and sauté until crisp and brown. Using slotted spoon, transfer bacon to small bowl. Add chicken, skin side down, to drippings in pot. Sauté until brown, about 8 minutes per side. Transfer chicken to large bowl. Add vegetables reserved from marinade to pot. Sauté until brown, about 10 minutes. Mix in flour; stir 2 minutes. Gradually whisk in reserved marinade liquid. Bring to boil, whisking frequently. Cook until sauce thickens, whisking occasionally, about 2 minutes. Mix in shallots, garlic, herb sprigs, and bay leaves, then broth. Return chicken to pot, arranging skin side up in single layer. Bring to simmer; reduce heat to medium-low. Cover pot and simmer chicken 30 minutes. Using tongs, turn chicken over. Cover and simmer until tender, about 15 minutes longer.

Step 4

Meanwhile, melt 3 tablespoons butter in heavy large skillet over medium heat. Add mushrooms; sauté until tender, about 8 minutes. Transfer mushrooms to plate. Melt remaining 1 tablespoon butter in same skillet. Add onions and sauté until beginning to brown, about 8 minutes. Transfer onions to plate alongside mushrooms; reserve skillet.

Step 5

Using tongs, transfer chicken to plate. Strain sauce from pot into reserved skillet, pressing on solids in strainer to extract all sauce; discard solids. Bring sauce to simmer, scraping up browned bits. Return sauce to pot. Add onions to pot and bring to simmer over medium heat. Cover and cook until onions are almost tender, about 8 minutes. Add mushrooms and bacon. Simmer uncovered until onions are very tender and sauce is slightly reduced, about 12 minutes. Tilt pot and spoon off excess fat from top of sauce. Season sauce with salt and pepper. Return chicken to sauce. (Can be made 1 day ahead. Cool slightly. Chill uncovered until cold, then cover and keep chilled.) Rewarm over low heat.

Step 6

Arrange chicken on large rimmed platter. Spoon sauce and vegetables over. Sprinkle with parsley.