Combine avocado, tomato, and 1 tablespoon TABASCO® Chipotle Sauce in a small bowl; stir in salt to taste and set aside.
Wrap tortillas in foil and warm in a 300°F oven for 10 minutes. Brush chicken with oil and season with salt. Grill over medium-high heat until browned and chicken is no longer pink inside, about 6 minutes per side.
Coarsely chop chicken and toss with remaining 3 tablespoons TABASCO® Chipotle Sauce. Serve immediately with warm tortillas, avocado salsa, cheese, lettuce, sour cream, and additional TABASCO® Chipotle Sauce, letting each person assemble his own tacos.
Makes 4 servings.