Lightly flour chicken pieces; rub with Dijon mustard.
In a cast iron roasting pan, melt butter and oil on medium-high heat, add onions and garlic; sear chicken for 3 minutes on both sides until golden. Add red wine and beef broth to deglaze; toss in salt, pepper, thyme, bay leaves, and mix well. Cover and bake at 350°F (180°C) for 1 hour. Remove from oven.
In a frying pan over medium heat, sauté bacon pieces for few minutes; add mushrooms, pearl onions and parsley, and continue to sauté, until the onions start to soften.
Lightly incorporate mixture into the roasting pan with the chicken. Let rest for few minutes before serving.