Put the pitted olives and 50 ml (1¾ fl oz) of olive oil in the bowl of a small food processor and blend well. Pour the paste onto a small tray and soak the sourdough slices, pressing down into the mixture on both sides of the bread to soak up all the oil.
Dehydrate the oil-soaked bread in an 80°C (175°F/Gas ¼–½) oven or dehydrator for approximately 6 hours or until the bread is dry and crisp. When dry, crumble the bread into rough 5 mm (¼ inch) pieces. Heat the remaining oil in a large non-stick frying pan over medium–high heat and fry the crumbs until crisp. Drain well, cool and store in an airtight container until required.