Discard the outer leaves of the lettuce and then tear it into pieces, adding to the bowl. Whisk the lime zest and juice and oil in a small bowl or jug and add a sprinkling of salt.
Open the pita breads up lengthways so that you have 4 very thin halves, and lay them on a baking sheet. Toast them in the oven for about 5 minutes to give them a bit of crunch; they will turn a golden brown color, but keep an eye on them as they might burn. Take the pita breads out and leave them to cool.
Halve the avocado, remove the stone and then using a spoon, scoop pieces of avocado out onto the bowl of lettuce. Dress the salad with the lime and oil dressing and add most of the chopped herbs before tossing with your hands to combine. Snip with scissors or break the crispy pita bread with your hands into rough triangles, and add most of the pieces to the salad and toss again before decanting to a serving bowl or platter. Scatter with remaining herbs and toasted pita.
Recipe courtesy of Nigella Lawson(Copyright 2004, Feast, Hyperion, All Rights Reserved)