Salmon Wellington

Name: Salmon Wellington
Ingredients: 1 (1 1/4-pound) piece salmon loin , skin and bones removed; 4 large light green Savoy cabbage leaves (6 ounces); Kosher salt; 1 pound shrimp , peeled and deveined; 2 egg whites; 1 teaspoon fish sauce; 3 tablespoons finely chopped fresh chives (about 1/4 ounce); 3 tablespoons finely chopped fresh dill (about 1/4 ounce); 1 1/2 teaspoons grated lemon zest (from 1 lemon); 2 sheets nori; 2 sheets frozen puff pastry , thawed (from a 17.3-ounce package); 3 egg yolks , beaten to blend; Lemon thyme or regular thyme leaves; Flaky sea salt