• 2 c. chicken stock
• 10 sprigs fresh flat-leaf parsley plus 2 tbsp. freshly minced flat-leaf parsley, divided
• 2 sprigs fresh thyme
• 1 bay leaf
• 4 oz. thick-cut bacon, cut into 1/4 -in. pieces
• 2 1/2 lb. boneless, skinless chicken thighs, trimmed of fat and cut in half crosswise
• Salt and freshly ground black pepper
• 5 tbsp. unsalted butter, divided
• 24 frozen pearl onions (about 1 c.), thawed and patted dry
• 8 oz. cremini mushrooms, wiped clean, stems trimmed, halved if small, quartered if large
• 2 garlic cloves, peeled and minced
• 1 tbsp. tomato paste
• 2 tbsp. flour
In a large saucepan over medium-high heat, combine all but 1 tablespoon of the red wine (reserving for later use), chicken stock, parsley sprigs, thyme and bay leaf and bring to a simmer. Cook until mixture is reduced to 3 cups, about 20 to 25 minutes. Discard herbs and reserve wine-stock mixture.
Meanwhile, in a large Dutch oven over medium heat, cook bacon, stirring occasionally, until browned, 7 to 8 minutes. Using a slotted spoon, transfer bacon to a paper towel-lined plate. Reserve 2 tablespoons bacon fat in a small bowl, and discard remaining fat.
Lightly season chicken with salt and pepper. Return Dutch oven to medium-high heat. Add 1 tablespoon bacon fat and heat until just smoking. Add half of the chicken, in a single layer, and cook until lightly browned, about 2 minutes per side. Transfer cooked chicken to a plate. Add remaining 1 tablespoon bacon fat and heat until just smoking, and repeat with remaining chicken.
Melt 3 tablespoons butter in now-empty Dutch oven over medium-high heat. When foaming subsides, add pearl onions and mushrooms and cook, stirring occasionally, until lightly browned, 5 to 8 minutes. Reduce heat to medium, add garlic and cook until fragrant, about 30 seconds. Add tomato paste and flour and cook, stirring frequently, until well-combined, about 1 minute.