For marinating chicken:
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.
For cooking chicken:
Transfer chicken pieces from marinade to paper towels to drain; pat dry. Strain
marinade; reserve vegetables and liquid separately.
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 20-30 minutes. Using
tongs, turn chicken over. Cover and simmer until tender, about 10-15 minutes
longer.
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.
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. Sprinkle with parsley. Serve with steamed whole
potatoes, or mashed.