Heat oven to 375 degrees. Heat oil and butter in a 6 qt pot over medium-high heat. Season chicken with salt and pepper and working in batches, sear chicken on all sides until browned, about 10 minutes. Transfer chicken to plate and set aside.

Add shallots and garlic to pan and saute, stirring occasionally, until golden, about 3-5 minutes.

Add wine, stock, mustard and thyme and bring to a boil. Return chicken to the pan with any juices, cover with a lid, and transfer the pot to the oven. Bake until chicken is cooked through, about 45 minutes, or until an instant read thermometer inserted into the thickest part of the meat reads 165 degrees.

Transfer chicken to a serving platter and tent with foil to keep warm. Return pot to stove and bring sauce to a boil. Cook, stirring occasionally, until reduced by half, 8-10 minutes. Spoon sauce over the chicken and garnish with the thyme.