Place the sugar and warm water together in a large bowl and stir to dissolve.
Sprinkle in the yeast and let this stand until frothy, for about 10 minutes.
Once it's frothy, stir in the 2 tablespoons of extra-virgin olive oil.
In a small bowl, mix the mashed potatoes with the salt.
Stir the potato mixture into the yeast mixture until very well combined. (a whisk will actually work better here)
Gradually stir in the flour, approximately 2 1/2 to 3 cups until the dough pulls away from the sides of the bowl.
Transfer the dough to a well floured work surface.
With floured hands knead in as much of the remaining flour as needed, until the dough is smooth and has a slightly sticky feel. About 8 minutes.
Place the dough in a large greased bowl, turning to grease all over.
Cover your dough with cling wrap and let it rise in a draft free space until it has doubled in size, for about 1 hour.
Grease 3, 8 inch cast iron skillets with oil and sprinkle with the coarse cornmeal.
Divide the focaccia dough into 3 equal portions and place into the prepared cast iron skillets.
Pat down the dough, stretching and pulling with your hands to reach the sides of the skillets
Cover the pans with greased cling wrap and and set aside to allow the dough to puff up to the rim of the pans for about 45 minutes to 60 minutes.
Meanwhile heat a tablespoon of olive oil in a medium sized frying pan.
Add the sliced red onions to the frying pan with a sprinkle of salt and pepper.
Cook over low heat while stirring occasionally, until the onions are soft and translucent, for about 5 minutes.
Remove from the heat and set aside to cool.
Meanwhile, place the raisins in a small bowl and cover with a little bit of hot water.
Allow to soak for about 10 minutes until the raisins plum up.
Drain the raisins and pat dry. Set aside.
Preheat the oven to 375 degrees F.
Remove the cling wrap from the risen dough.
Scatter first the raisins over the dough then top with the chickpeas, the sautéed onions and using your fingers gently press down into the dough while making indentations.
Drizzle the tops with a little olive oil. (about 1 teaspoon over each focaccia)
Bake in the preheated oven for about 25 to 30 minutes, until the edges are crusty and the focaccia is golden brown.
Sprinkle a pinch or 2 of coarse sea salt over each focaccia while still warm.
Allow to cool a little before slicing and serving.