How to Make It
Preheat the oven to 325°. On half of a heavy-duty 2-by-1 1/2-foot sheet of foil, mound the onions and potatoes. Add 1/4 cup of the wine, the olive oil and bay leaves and season with salt and pepper. Fold the foil over the vegetables; seal the edges. Transfer to a rimmed baking sheet and bake for about 1 hour and 20 minutes, or until the vegetables are tender. Peel and slice the onions.
Meanwhile, in a medium saucepan, simmer the remaining 3 cups of wine with the mustard and molasses over moderately low heat, stirring, until reduced to 1/2 cup, about 35 minutes. Season with salt and pepper.
Season the chicken with salt and pepper. Put in a steamer basket, cover and steam over moderate heat for 8 minutes.
Reheat the sauce. Spoon the vegetables onto plates, discarding the bay leaves. Set the chicken breasts alongside and spoon the sauce over them. Sprinkle with the parsley and serve.