Wash and clean the citrus fruits and use a sharp knife to scoop out the flesh.
In a pot, add equal quantity of water and sugar with a splash of vanilla and add in the peels. Let this simmer for 30-40 minutes.
Get the peels out and allow them to dry at room temperature on a lined baking sheet. You can also toss them in some granulated sugar after this if you want to.
After a day, once the peels have hardened and turned slightly chewy, chop them up into small bits like I did, or even finer if you want to.
Notes
Since you're using the actual peel of the fruits here, it is a great idea to choose organic fruit if you can.
Also make sure to nicely clean and scrub the fruits before you use the peel for this recipe. This will help remove any traces of wax or pesticides on the surface.
Remove only the peel, and try to stay away from as much of the white pith portion as you can- since it can be quite bitter.
To cut down the bitterness of the peels, you can boil them in a pot of water for 15 minutes, strain the water and then repeat the step again before you use the peels for the recipe.