Salt, pepper Bone skin and split chicken breasts, then flatten into cutlets. Saute chicken in 2 tablespoons butter until cooked on both sides. Remove from pan and keep warm. Melt remaining butter in skillet. Add onion and cook until tender. Add wine and mustard and simmer until mixture is reduced by half. Add whipping cream and simmer until sauce is thick enough to coat spoon. Strain, then add rosemary, thyme and tarragon. Season to taste with salt and pepper. Pour over chicken breasts.