Tip the flours into a large bowl and stir in the yeast and salt. Pour in the oil and enough warm water to make a soft but not sticky dough, adding more water or flour if needed.
Knead until smooth and elastic. Put into an oiled bowl, cover with a polythene bag and leave in a warm place for an hour until doubled in size.
Turn the dough onto a floured surface and knead for a minute before adding the cooked onion, extra oil and chopped olives.
Shape the dough into a round loaf and place on an oiled baking sheet. Cover again and leave in a warm place to rise for 30 minutes.
Preheat oven to 180 C, Gas 4. When the bread has had its 30 minutes put into the oven and bake for 45 minutes or until the base sounds hollow when tapped. If you want a shiny finish lightly brush the top with oil and return to the oven for a minute.