Saute mushrooms in butter in a large ovenproof saute pan over med-high heat, stirring frequently. When they soften and give off liquid, reduce heat to med, cook until liquid evaporates.
Stir in the first 1/2 cup of red wine. increase the heat to high and boil until most of the wine evaporates, remove and set aside. wipe out pan and return it to the stove top.
Brown the chicken in butter and oil(may need to do this in batches) in the saute pan over med heat, remove and set aside.
Saute the pancetta in the pan drippings, cooking until it begins to brown. add the onion and fennel, cooking until the onion softens and fennel begins to brown. Stir in garlic and cook 2-3 minutes more. Increase heat to high and stir in the next 1/2 cup wine and sage. Remove from heat and add the sauteed mushrooms.
Return the chicken to the pan, cover tightly, transfer to the oven and bake until the meat is tender and the internal temp is 170°F, about 40 minutes. Remove from heat oven and stir in vinegar.
While chicken is in the oven prepare papardelle according to package directions; drain.
Serve parpardelle with chicken and mushroom sauce.