Toast the couscous in a saucepan over medium heat until evenly golden, being careful not to burn it. Add 1 cup (250ml) water and a pinch of salt and cook until tender, 5 to 7 minutes.
Meanwhile, heat 1 tablespoon oil in a skillet over medium heat. Add the chorizo and cook until almost crispy, about 3 minutes. Add the shallot and cook until soft. Stir in the garlic and preserved lemon peel.
Stir the couscous into the chorizo mixture. Just before serving, drizzle with the remaining 2 tablespoons oil. Stir in the chives and parsley and season with salt and pepper.
Wash the lemons very well. Cut each lemon lengthwise in quarters without slicing all the way through, leaving the lemons whole. Place the lemons in a sterilized jar. Add the salt, lemon juice, peppercorns and kaffir lime leaves and mix well. Add more lemon juice if needed to just cover the lemons. Close with a lid and refrigerate. Stir the lemons every day or two to help dissolve the salt. Allow the lemons to cure for at least 1 week. Rinse under cold water before using.