Start by preparing the mashed potato: peel, chop, boil and mash about 4 medium sized potatoes to make 2 cups of mashed potato. Set aside and allow to cool until warm.
Mix yeast with warm water and set aside for 5 minutes to dissolve and begin to activate.
In a large mixing bowl, mix mashed potato, flour, olive oil, salt and water/yeast mixture, until a shaggy dough comes together.
Tip dough out onto a lightly floured surface and knead for 5-10 minutes, sprinkling with a little more flour as needed to prevent the dough becoming overly sticky. The finished dough should be smooth, elastic and a bit sticky.
Return dough to an oiled bowl, cover with a tea towel and set aside in a warm place to rise for 1 hour, until the dough has about doubled in size.
Knock down the dough with your fist, then stretch to a large oval shape on an oiled baking tray. Use your fingers to deeply dimple the dough, cover and set aside to rise for another hour.
At this time, prepare your foccacia topping by mixing everything together in a bowl and setting aside to marinate.
Preheat oven to 200C (390F).
When the dough has finished proving, spread the foccacia topping evenly over the surface of the loaf and drizzle any remnants of oil in the bowl over the loaf too. Use your fingers to push individual chunks down into the dough a bit, to ensure everything sticks once the loaf is baked.
Grind over a little sea salt if desired (remembering the olives are salty too).
Bake for 30 minutes, until the loaf is golden brown.
Cool for 10-15 minutes before slicing into large wedges to serve.