I make this every year for cheap-but-wonderful Christmas presents for family and friends. And I always make sure that there is enough made so that I can keep at least six jars for myself. This is brilliant on cheese sandwiches, in a chili, or to pep up some chicken wings.
Surprisingly, both cilantro and basil freeze very well. After cutting the leaves, preferably in the early morning while they are freshest, we mix them with a small amount of olive oil... just enough to coat the leaves. They are then packed into freezer bags and frozen for later use. The olive oil makes it really easy to separate the frozen leaves and also adds an extra flavor to the mix.