Place the avocado in a bowl and pour over the lime juice. Add the shallots, tomatoes, chilli, 1 crushed garlic clove, and 1 tbsp of olive oil; gently mix together. Season with freshly ground black pepper.
Toss the kidney beans with the remaining garlic and oil. Toss in the watercress and season well. Arrange the kidney bean and watercress salad onto the toasted pitta breads and top with the chunky guacamole.