Wash the citrus. Remove the rind, scrape away attached flesh and trim unusually thick pith, leaving enough for a substantial peel. Cut into strips about 6 mm wide.
Cover the peel with fresh water. Boil for 5 minutes, then drain. Repeat twice, using fresh water each time, for three blanching rounds.
Dissolve 2 cups sugar in 2 cups water. Add the peel, bring just to the boil, then lower to a gentle simmer.
Cook for about 40–60 minutes until tender and translucent at the edges. Thin lemon peel may finish earlier; judge by texture.
Lift out with a slotted spoon or drain through a sieve, reserving the citrus syrup.
Spread the drained peels in one layer on baking parchment. Air-dry overnight or for at least a couple of hours. Let them cool and lose excess surface syrup before packing.
For a sugar-coated finish, toss the cooled, slightly tacky peels in extra sugar and shake off excess. Leave uncoated for a glossy finish.
Store the finished, cooled peels in an airtight container. Chop into small pieces for the Christmas fruit-soaking mixture.