In a bowl, toss together bread, tomatoes, cucumber, red onion and avocado.

In a separate bowl, whisk together vinegar, garlic, mustard, salt and pepper. Slowly, in a gradual stream, whisk in olive oil until emulsified. Pour over dressing, tossing gently until evenly coated. Let stand at room temperature for 20 minutes.

Toss again, add fresh basil and serve.