Peppercorn-Cilantro Flavor Paste
This peppercorn-cilantro root paste from Jeffrey Alford and Naomi Duguid may sound exotic but it's a classic Thai trick for imparting a lot of oomph without a lot of ingredients or expense.
Place the peppercorns in a mortar with the garlic and pound to a paste.
Add the cilantro roots and salt and pound to a paste. This will take 5 to 10 minutes. If you have a small blender or other food grinder that can produce a smooth paste, you can use it instead. (We tend to toss in a few cilantro stems along with the roots when we make this paste—just for good measure.)
Stir in the fish sauce.
Use the paste immediately or store in a well-sealed glass jar. This keeps for up to 4 days in the refrigerator.