The Best Recipe, by Editors of Cook's Illustrated Magazine
Rapid-rise yeast reduces the preparation time by more than an hour. If you use an equal amount of regular active dry yeast instead, let the sponge in step 2 develop for 30 minutes rather than 20, and increase the first and second rises to 1½ hours each.
Makes One 1 5½ X 10½-Inch Rectangle Or Two 8-Inch Rounds
• 1 medium baking potato (about 9 ounces), peeled and quartered
• 1½ teaspoons rapid-rise yeast
• 3½ cups unbleached all-purpose flour
• 1 cup warm water (105 to 115 degrees)
• 2 tablespoons extra-virgin olive oil, plus more for oiling bowl and pan
• 1¼ teaspoons salt
• 2 tablespoons extra-virgin olive oil
• 2 tablespoons fresh rosemary leaves
• 3/4 teaspoon coarse sea salt (or 1¼ teaspoons kosher salt)
1. FOR THE DOUGH: Bring 1 quart water to boil in small saucepan; add potato and simmer until tender, about 25 minutes. Drain potato well; cool until it can be handled comfortably and put through fine disk on ricer or grate through large holes on box grater. Reserve 1 1/3 cups lightly packed potato.
2. Meanwhile, in large bowl of electric mixer or workbowl of food processor fitted with steel blade, mix or pulse yeast, 1/2 cup flour, and 1/2 cup warm water until combined. Cover tightly with plastic wrap (or put workbowl lid on) and set aside until bubbly, about 20 minutes. Add remaining dough ingredients, including reserved potato. If using mixer, fit with paddle attachment and mix on low speed until dough comes together. Switch to dough hook attachment and increase speed to medium; continue kneading until dough is smooth and elastic, about 5 minutes. For food processor, process until dough is smooth and elastic, about 40 seconds.
3. Transfer dough to lightly oiled bowl, turn to coat with oil, and cover tightly with plastic wrap. Let rise in warm, draft-free area until dough is puffy and doubled in volume, about 1 hour.
4. With wet hands (to prevent sticking), press dough flat into generously oiled 15½ x 10½-inch jelly-roll pan. If the dough resists going into the corners (and it probably will), cover it with a damp cloth and let it relax for 15 minutes before trying to stretch again. Or, if making rounds, halve and flatten each piece of dough into 8-inch round on large (at least 18 inches long), generously oiled baking sheet. Either way, cover dough with lightly greased or oil-sprayed plastic wrap; let rise in warm, draft-free area until dough is pufly and doubled in volume, 45 minutes to 1 hour.
5. Meanwhile, adjust oven rack to lower-middle position and heat oven to 425 degrees.With two wet fingers, dimple risen dough at regular intervals. The dimples (there should be about 2 dozen) should be deep enough to hold small pieces of topping, herbs, and/or pools of olive oil.
6. FOR THE TOPPING: Drizzle dough with oil and sprinkle evenly with rosemary and coarse salt, landing some in pools of oil.
7. Bake until focaccia bottom(s) are golden brown and crisp, 23 to 25 minutes. Transfer to wire rack to cool slightly. Cut rectangular focaccia into squares or round focaccia into wedges; serve warm. (Focaccia can be kept on counter for several hours and reheated just before serving. Or, wrap cooled focaccia in plastic and then foil and freeze for up to 1 month; unwrap and defrost in 325-degree oven until soft, about 15 minutes.