Shrimp and cod burgers

12 ounces medium shrimp, peeled, deveined, and cut into chunks

8 ounces cod, cut into chunks

3/ 4 cup fine fresh bread crumbs

1/4 cup drained capers, rinsed

2 medium scallions, thinly sliced

3 tablespoons chopped fresh flat-leaf parsley

1/4 cup fresh lemon juice (1 to 2 lemons)

1 1/4 teaspoons coarse salt

3/4 teaspoon freshly ground pepper

Vegetable oil, for brushing

4 hamburger buns

Red leaf lettuce, for serving

Tarragon Tartar Sauce
, for serving (optional )

Lemon wedges, for serving

Process half of the shrimp in a food processor until a paste forms. Add the cod, remaining shrimp, and the bread crumbs, capers, scallions, parsley, lemon juice, salt, and pepper. Pulse until just combined (do not overprocess).
Using dampened hands, shape into 4 patties. Refrigerate, covered, until cold and firm, about 1Ë™ hours (or overnight).
Preheat the grill to medium-high (if using a charcoal grill, coals are ready when you can hold your hand above grill for just 3 to 4 seconds). Brush the grill and the burgers with oil.
Grill, flipping once, until cooked through, about 3 minutes per side. Toast the buns on the grill during the last minute of cooking, if desired. Serve the burgers on the buns; top with lettuce. Serve with tartar sauce, if desired, and the lemon wedges.

M A K E S 4