Put 12 ounces rinsed, quartered citrus peels (including white pith; if using peels reserved from another use, scrape off any clinging fruit) in a 2- to 3-quart pan and add water to cover. Boil over high heat for 1 minute, then reduce heat and simmer for 30 minutes. Drain; repeat process twice. When peels are cool, scrape away any white pith thicker than 1/4 inch. Cut peels lengthwise into strips (1/4 in. wide). In pan, combine 1 1/2 cups granulated sugar, 1/4 cup light corn syrup, and 1 1/2 cups water. Set over medium-high heat and cook, swirling occasionally, until sugar is dissolved. Add peels, reduce heat, and simmer, stirring occasionally, until translucent, about 1 hour. Transfer peels to a wire rack set over waxed paper. Let stand until barely moist to touch, about 2 hours. Roll peels in superfine sugar and set on a clean wire rack; let dry completely, 8 hours or overnight. Store airtight, covering peels completely with sugar, up to 2 months.