8-16 oz. floury (baking) potatoes, peeled and cut into chunks
Put the potatoes and 4 cups water in a sauce pan and bring to boil. Add 1 teaspoon salt and cook, half covered, until the potatoes are very tender (this doesn't take long!). Drain the potatoes, SAVE THE POTATO WATER, and mash the potatoes well. Measure out 3 cups (750ml) of the reserved potato water. Add extra water if needed to make 3 cups. Place the water and mashed potatoes in the bowl you plan to mix the bread dough in. Let cool to lukewarm (70-80°F/21 - 29°C) – stir well before testing the temperature – it should feel barely warm to your hand. You should be able to submerge you hand in the mix and not be uncomfortable.
Add 2 cups of the unbleached all-purpose flour and stir until all the flour has been incorporated (now you have used 4 cups of the possible 8 ½ cups suggested by the recipe). Turn the dough out onto a generously floured surface (I used a really big bowl, so I just left it in the bowl) and knead for about 10 minutes, incorporating flour as needed to prevent sticking. The dough will be very sticky to begin with, but as it takes up more flour from the kneading surface, it will become easier to handle; the kneaded dough will still be very soft. Place the dough in a large clean bowl or your rising container of choice, cover with plastic wrap or lid, and let rise about 2 hours or until doubled in volume.
To make focaccia:Flatten out the dough to a rectangle about 10 x 15 inches with your palms and fingertips. Tear off a piece of parchment paper or wax paper a little longer than the dough and dust it generously with flour. Transfer the focaccia to the paper. Brush the top of the dough generously with olive oil, sprinkle on a little coarse sea salt, as well as some rosemary leaves, if you wish and then finally dimple all over with your fingertips. Cover with plastic and let rise for 20 minutes.
Preheat oven to 450°F(230°C)
For rolls: Dust risen rolls with a little all-purpose flour or lightly brush the tops with a little melted butter or olive oil (the butter will give a golden/browned crust). Bake rolls until golden, about 30 minutes. Transfer the rolls to a rack when done to cool.
For foccaia:Place a baking stone or unglazed quarry tiles, if you have them, if not use a no edged baking/sheet (you want to be able to slide the shaped dough on the parchment paper onto the stone or baking sheet and an edge complicates things). Place the stone or cookie sheet on a rack in the center of the oven and preheat to 450°F/230°C.
If making foccacia, just before baking, dimple the bread all over again with your fingertips. Leaving it on the paper, transfer to the hot baking stone, tiles or baking sheet. Bake until golden, about 10 minutes. Transfer to a rack (remove paper) and let cool at least 10 minutes before serving.