This recipe, based on traditional Brazilian recipes for sweets and conserves made from the peel of almost any type of citrus fruit, is translated and adapted from the website Ptitchef. Although the recipe calls for the peel of the citrus called rangpur or mandarin-lime in English and limão-cravo in Portuguese it can very easily be adapted to any citrus fruit. If the fruit you want to use is very thin skinned, you need do nothing to prepare the skin other than wash it well. If the fruit is one that has a thick white pulp under the outer surface of the peel, you must remove that, leaving only the outer peel, fragrant and colored. Otherwise, you'll have a very bitter "sweet."
RECIPE - Crystalized Mandarin-Lime Peel (Casquinha Cristalizado de Limão-Cravo)
12 large, whole mandarin-limes (or equivalent weight of any other citrus fruit)
1 lb (500 gr) granulated white sugar
1 cup (250 ml) water
Thoroughly wash the whole fruit. Cut in half, and squeeze out all the juice, reserving the juice for another use. Remove the remaining pulp and any bitter white inner peel that may exist - use the tip of a spoon. Cut the outer peel that remains into strips about 1/2 inch (1 cm) wide and 1 1/2 inches (3 cm) long. Put the sliced peel in a mixing bowl, cover with lots of fresh water and let sit for a few hours. Drain.
In a medium saucepan, add the drained peel, cover with water, bring to a boil rapidly, then drain the peels in a sieve or colander and refresh with cold water. Repeat this operation two or three more times, or until all trace of bitterness is removed (taste a small piece to verify). Drain again and reserve.
In a heavy-duty sauce pan combine the sugar and 1 cup water and heat over medium heat. Stir to completely dissolve the sugar and bring to a slow boil. Continue to cook until the syrup reaches the thin-thread stage. Add the reserved peel and cook for about 5 minutes more. Remove from heat. If you wish to serve preserved peels in syrup, the dish is complete.
To make crystalized peels, remove them from the syrup with a slotted spoon (reserving the syrup for another use). Drain thoroughly in a sieve for at least 30 minutes. Spread a layer of granulated sugar on a cookie sheet, then roll the peels in the sugar to completely cover them.
Remove the peels from the cookie sheet with tongs and place on a sheet of wax paper, making sure that they are separated to avoid clumping. Let dry overnight. When completely dry, place in a cookie tin or other dry container until ready to use. Can be served as is, or used to decorate cakes and other desserts.