Candied Grapefruit Peel

The corn syrup helps keep the candied peel supple. Note that Karo and similar corn syrups are not high-fructose corn syrup. You can read more at my post Why and When To Use, or Not Use, Corn Syrup.) You could use Golden of Agave syrup in its place, or leave it out. A candy thermometer is very helpful to use here. I have an old-school thermometer that I've had for decades that I use (as shown in the post) but they can break, so recommend one with a metal back. Thermapen probe-type thermometers are great but you have to continue to dip the probe into the syrup while the peel is cooking. If you don't have a candy thermometer, you can make the peel but you'll have to gauge when it's ready by sight, which isn't as accurate. The peel is done (in step #2) when the syrup is almost all reduced and the syrup becomes white and foamy. But do keep an eye on it if going that route as it's very easy, and emotionally painful, if you go this far with candying the peel, and burn it in the last few seconds.

Servings servings (approximately)

4 grapefruit halves, from two grapefruits, scraped clean with a soup spoon
3 cups (600g) sugar, plus 3/4 cup (150g) of sugar for finishing the candied peels
2 1/2 cups (625ml) water, plus additional water for blanching the grapefruit peels
2 tablespoons light corn syrup

Cut the grapefruit rinds into strips about 1/4-inch, or slightly less. (About .5cm.) Blanche the peels by putting them in a large, non-reactive pot. Cover with water and bring to a boil. Reduce heat and simmer for 10 minutes. Drain the peels, put them back in the pot, cover with water and bring to a boil. Let simmer for 2-3 minutes, then drain.
Place the peels back in the pot. Attach a candy thermometer to the side of the pot and add the 3 cups sugar, 2 1/2 cups water, and corn syrup. Cook over medium-high heat until the temperature reaches 225ºF (107ºC.) Turn off the heat and use a slotted spoon to transfer the grapefruit peels onto a wire cooling rack set over a baking sheet, separating the peels into a single layer, Let the peels sit overnight. (You can reserve the syrup and use it for sweetening iced tea or lemonade, or another purpose.) If you don't have a wire rack, you can use a colander or mesh strainer set over a bowl, gently turning the peels several times, to help them drain.
The following day, put the remaining 3/4 cup sugar in a medium bowl. Working on batches, place a handful of the candied peels in the bowl of sugar and toss to coat them thoroughly. Using your hands, gently (but with determination) shake off the excess sugar. You want to avoid any clumps of sugar, if possible. Set the sugared peels on the cooling rack again, keeping them separate, and coat the remaining candied grapefruit peels with sugar, spreading them out on the wire rack. Let stand at room temperature a few hours to dry, before serving.

Notes

Storage: I generally keep the peel at room temperature if I plan to serve it within the next few weeks. You can refrigerate it in a container, although over a period of time, depending on your refrigerator, it can get damp (and subject to mold) or too hard. If the latter, you can chop it and rehydrate it in water, and use it in a cake or cookie dough, or fold into ice cream.