Heat a cast iron skillet in a 240C/475F oven.

Mix together all of the ingredients above and whisk until you have a smooth batter. The batter should be thinner than crepe batter.

Brush a generous amount of oil on the pan. The oil should be smoking. Pour the batter on the hot plancha and cook with the oven door slightly ajar for the first couple of minutes and then turn on the grill (broiler) to maximum so that the socca can get crisp on top.

Keep an eye on it as it bubbles and rises, but make sure that it doesn't burn. It should only be slightly brown.

It should be slightly crisp on the outside, but creamy on the inside even though it should be about 1/8 of an inch or 3mm thick.

Cut it into squares.

I tried making it on the stovetop and it works, but you have to cook it like a crepe and turn it over. I prefer the oven method.