Portobello Mushroom Burgers With Dressing

1 cup mayonnaise
1/3 cup shopped fresh basil
2 tablespoons Dijon mustard
1 teaspoon fresh lemon juice
1/3 cup olive oil
1 tablespoon minced garlic
6 to 5-inch-diameter portobello mushrooms -- stems removed
6 to 4-inch-diameter hamburger
6 large romaine lettuce leaves
1 1/2 cups mesquite wood chips -- soaked in cold water 1 hour (optional)

Mix first 4 ingredients in small bowl. Season with salt and pepper.

Whisk olive oil and garlic in another small bowl.

Prepare barbecue (medium-high heat). When coals turn white, drain chips, if using, and scatter over coals. When wood chips begin to smoke, brush mushroom caps on both sides with garlic oil. Season with salt and pepper.

Grill mushrooms until tender and golden brown, about 4 minutes per side. Transfer to platter; cover with foil to keep warm.

Grill hamburgers.

Top each with 1 mushroom, then 1 lettuce leaf.

Spoon some basil-mustard sauce.

Pass remaining basil-mustard sauce separately.

6 servings.