Remove the outer orange rind without the pith, and cut it in neat thin strips. Cover the orange rind with a little cold water; stew till just tender; then strain. Squeeze the orange and lemon juice into the sauce, add the orange rind. Reheat, add the wine (if used), the redcurrant jelly, season with salt, pepper and sugar to taste.
Serve with roast duck, goose or wild duck.