To prepare with a food processor:
Heat a 7-inch skillet over medium-high heat. Add the coriander seeds and dry-roast, sliding the skillet back and forth over the burner, until seeds are fragrant, about 3 minutes. Transfer the seeds to a small bowl to cool and repeat with the peppercorns. When cool, grind the coriander seeds and peppercorns separately in an electric spice or coffee grinder and transfer to separate bowls.
Fit the food processor with a steel blade. Add the sea salt, garlic, and cilantro roots and stems and pulse until finely minced, scraping down the side of the bowl frequently. Add the ground spices and process to a paste. Transfer to a jar, seal, and refrigerate.
Courtesy of Su-Mei Yu's Cracking the Coconut (Morrow, 2000)