Step 1

Toast 2 Tbsp. sesame seeds in a dry small skillet over medium heat, tossing often, until evenly dark brown, 6–9 minutes.

Step 2

Coarsely crush sesame seeds with mortar and pestle or very coarsely grind in spice mill; transfer to a medium bowl. Add ½ cup mayonnaise, ½ cup plain whole-milk Greek yogurt, ¼ cup finely chopped chives, zest of 1 large lemon, 1 Tbsp. fresh lemon juice, 1 tsp. Diamond Crystal or ½ tsp. Morton kosher salt, 1 tsp. garlic powder, 1 tsp. onion powder, and 3 Tbsp. water to bowl; whisk to combine. Finely crumble one .35-oz. package seasoned toasted seaweed snacks over and whisk again to combine. Dressing should be thick but pourable; thin with more water (up to 1 Tbsp.) if needed (makes about 1¼ cups).Do ahead: Dressing can be made 2 days ahead. Cover and chill.

Step 3

Trim root end of 1 small head of iceberg lettuce (about 1 lb.) and discard any wilted outer leaves. Cut into quarters lengthwise, then cut each quarter crosswise into 3" pieces. Transfer to a platter. Tuck 2 avocados, cut into 1" pieces, around lettuce and drizzle 1 Tbsp. fresh lemon juice over; season with kosher salt.

Step 4

Spoon half of dressing over salad. Season with freshly ground pepper and top with thinly sliced seasoned toasted seaweed snacks. Serve with remaining dressing alongside.