Combine Extra Melt Cheese Sauce and mashed avocado in food processor. Pulse continuously while drizzling in lemon juice and water. Continue processing until smooth and light green. Transfer dressing to squeeze bottle. Hold chilled until service.
To make croutons, toss bread with olive oil, salt and pepper. Grill bread chunks on hot grill about 3 minutes, turning to mark all sides; set aside to cool.
Trim ends of lettuce heads. Halve them the long way; cut halves into quarters. Place lettuce onto hot grill cut-sides down. Grill 30 seconds or until charred.
Place 2 lettuce quarters onto each plate. Drizzle avocado dressing over lettuce. Garnish with bacon, tomatoes, croutons and chives.