FOOLPROOF FOCACCIA

Steps:

• FOR THE DOUGH:.
• Boil potato in water and simmer until tender (about 25 minutes).
• Drain potato well and cool.
• Grate potato through large holes on box grater, fine disk on ricer or food processor.
• Reserve 1-1/3 cups lightly packed potato.
• Meanwhile, In food processor mix or pulse yeast, 1/2 cup flour, and 1/2 cup warm water until combined.
• Cover tightly with plastic wrap and set aside in a warm place, until bubbly (about 20 minutes).
• Add remaining dough ingredients (including the remaining 3 cups flour), including reserved potato.
• Process dough for about 40 seconds until it's smooth and elastic.
• Transfer dough to lightly oiled bowl, turn to coat with oil and cover tightly with plastic wrap.
• let rise in warm area until dough is puffy and doubled in volume (about an hour).
• With wet hands (to prevent sticking) press dough flat into oiled or sprayed with Pam 15 1/2 by 10 1/2 jelly roll pan (I sprinkle a little flour on top of dough and gently pat it into shape. I don't make it quite as large, since I like it really thick).
• Cover dough with lightly greased plastic wrap (dough will stick otherwise) and let rise in warm area, about 45 minutes to an hour, until dough is puffy and doubled.
• Preheat oven to 425°F.
• Adjust oven rack to lower middle position.
• With two wet fingers, dimple risen dough at regular intervals.
• TOPPING:.
• Drizzle dough with oil, and sprinkle evenly with the rosemary, salt, landing some in pools of oil.
• Bake until focaccia bottom is golden and crisp, 23-25 minutes.
• Yields: one 15 1/2 by 10 1/2 inch rectangle or 2 8 inch rounds.
• *Note: focaccia can be kept on counter for several hours and reheated just before serving.
• Or, wrap cooled focaccia in plastic wrap, and then foil and freeze for up to 1 month (unwrap and defrost in 325°F oven until soft, about 15 minutes).
• •VARIATIONS:.
• Parmesan Focaccia: substitute 2/3 cup grated Parmesan cheese for the rosemary and coarse sea salt.
• Focaccia with Black Olives and Thyme: substitute 1 teaspoon fresh thyme leave and 24 pitted large black olives (one per oil-filled dimple) for rosemary.