Thin strips of candied peel come out chewy; thicker ones are softer, making them better for dipping in chocolate.
Score citrus into quarters and peel off skin. Trim off a little of the white pith, then cut peels into long strips. Place peels in a small stainless-steel saucepan. Cover with cold water and bring to a boil. Simmer 8 to 10 minutes, drain, and repeat twice more. Drain well.
Wash pan; combine water, sugar, and corn syrup. Stir over medium heat until dissolved. Bring to a boil; add peels.
Turn heat down to low and cook until peels are translucent and syrup has been almost completely absorbed.
Drain peels in a colander. If desired, roll in sugar or dip in chocolate. Using tongs, remove to a parchment-lined baking sheet to dry. Store in an airtight container.