Mix the white flour with the wholemeal flour and salt and make a well in the middle.
Heat 100 ml (3.4 fl. oz) of water slightly and add the yeast.
Leave the yeast for 10 minutes then pour it over the flour.
Start kneading gently and gradually add the rest of the water and the oil.
You should get a soft and non-sticky dough. If necessary, add more flour or water.
Grease a large baking tray with olive oil.
Place the dough in the pan and turn it several times so that it is oiled on all sides.
Cover the dough with cling film and leave to rise in a warm place for 1 hour until doubled in volume.
Julienne the onion and chop the parsley, but not too finely.
After an hour, using your fingers, gently roll the dough in the pan so that it reaches the edges.
Make small indentations all over the dough.
Sprinkle coarse salt on top, then the onion and parsley.
Pour over the olive oil.
Leave the dough to rise for another 45 minutes.
Preheat the oven to high (200 degrees Celsius or 390 Fahrenheit) and bake the onion focaccia until nicely browned on top, about 25-30 minutes.
It's delicious hot or cold.
Enjoy!