Wash the fruit; cut into thin slices, remove any seeds and cut each slice into 1/8" (0.3 cm) strips. Measure the grapefruit and orange strips (there should be about 7 c./1.75 L of grapefruit and about 5 3/4 c./1.5 L of oranges).

Place the fruit in a large kettle or saucepan and add enough water to cover. Bring to the boil; drain; repeat.

Add the 1 L (4 cups) water to the pan after the second draining; cook, uncovered, 1½ hours or until the fruit is tender. Cook over medium heat until thick, about another 1½ hours, stirring often.

If using, add the chopped nuts and liqueur; pour into hot sterilized jars. Seal at once.

Maybe the saying should be An orange a day keeps the doctor away!