Dissolve the arrowroot in a little water and whisk into the syrup until it is thick enough to coat the back of a spoon. Remove from the heat, stir in the lime zest and set aside to cool.

Pick out and discard the ginger. Stir the lime juice into the syrup; let cool completely. Meanwhile, using a sharp knife, peel all of the citrus fruits and cut off all of the bitter white pith.

Just blend one ripe avocado, the juice of two limes, a clove of garlic, a handful of cilantro leaves, and salt to taste. Add ...