Step 1

Preheat oven to 350°F. Heat oil in a large Dutch oven over medium heat. Add pancetta and cook, stirring occasionally, until browned, 2 to 4 minutes. Using a slotted spoon, transfer to a paper towel-lined plate. Season chicken with salt and pepper. Cook, skin side down, until golden brown, 5 to 7 minutes. Transfer to plate.

Step 2

Increase heat to medium-high. Add mushrooms and cook, stirring occasionally, until browned, 6 to 8 minutes. Reduce heat to medium-low and add onions, leeks, and garlic. Cook, stirring occasionally, until light golden brown and tender, 8 to 9 minutes. Add flour and cook, stirring, 1 minute. Gradually add wine, stirring constantly. Add stock, mustard, thyme, and bay leaves; bring to a simmer.

Step 3

Return pancetta and chicken (skin sides up) to pot; cover and transfer to oven. Cook until chicken is fork-tender and cooked through, 1 hour and 15 minutes to 1 hour and 30 minutes. Discard thyme and bay leaves. Serve topped with tarragon