How to Make It
Shuck the clams over a medium bowl. Scrape and clean 20 of the best half shells and refrigerate.
Cut the clams into 1/2 -inch pieces and place them in a clean bowl. Strain 1/4 cup of the clam liquor over the clams. Add the onion, lime juice, jalapeños, tomato and cilantro and season with pepper. Cover and refrigerate for at least 1 hour or for up to 2 hours.
Nestle the clam half shells on a bed of finely crushed ice. Spoon the clam seviche and any clam liquor into the cleaned shells. Garnish with cilantro sprigs and serve with lime wedges.