Roughly chop the beetroot. Drain and rinse the chickpeas. Put these in a food processor with the garlic, coriander, lemon juice and olive oil. Blitz until fairly smooth. Taste and add freshly ground pepper, and salt if you wish.
Divide the salad leaves between 6 plates. Spoon a little houmous onto each plate and scatter with a few olives. Drizzle a little oil over the leaves and sprinkle with a little black pepper, and salt, if you wish.
Toast the pittas, cut into wedges and serve with the houmous.