2 tablespoons canola oil or peanut oil
2 tablespoons minced lemongrass (from bottom 3 inches of about 4 stalks)
2 garlic cloves, minced
4 ounces fresh shiitake mushrooms, stemmed, caps chopped
1 teaspoon coarse kosher salt, divided
1 3/4 pounds ground pork shoulder (Boston butt)
2 tablespoons soy sauce, divided
3 teaspoons Asian sesame oil, divided
3/4 teaspoon cracked black pepper
1/2 cup hoisin sauce*
1 tablespoon minced peeled fresh ginger
1 tablespoon unseasoned rice vinegar
1 teaspoon hot chili sauce (such as sriracha)*
Nonstick vegetable oil spray
2 heads of Bibb lettuce, cored, leaves separated
1 cup matchstick-size strips red bell pepper
1 cup matchstick-size strips peeled carrot
1/3 cup fresh cilantro leaves
Preparation

Heat oil in large skillet over medium-high heat. Add lemongrass and garlic; saute 2 minutes. Add mushrooms. Sprinkle with 1/2 teaspoon coarse salt; saute until mushrooms are tender, about 4 minutes. Remove from heat; cool in skillet.

Place pork in large bowl. Mix in 1 tablespoon soy sauce, 1 teaspoon sesame oil, cracked pepper, and 1/2 teaspoon coarse salt, then fold in mushroom mixture. Using 2 generous tablespoonfuls for each, shape into 18 patties, each about 2 1/4 inches in diameter; arrange on plastic-lined baking sheet.

Whisk hoisin sauce, ginger, vinegar, chili sauce, and remaining 1 tablespoon soy sauce and 2 teaspoons sesame oil in small bowl for sauce. DO AHEAD: Burgers and sauce can be made 6 hours ahead. Cover separately; chill.

Spray grill rack with nonstick spray. Prepare barbecue (medium-high heat ). Grill burgers until cooked through, about 3 minutes per side. Arrange burgers on platter; set out sauce. Place lettuce, bell pepper, carrot, and cilantro in separate bowls. Serve, allowing guests to wrap burgers in lettuce and add sauce and vegetables as desired.