TOMATO FOCACCIA

Steps:

• Generously cover potato with salted cold water (1 teaspoon salt for 3 cups water) in a small heavy saucepan and simmer, uncovered, until just tender, 10 to 15 minutes. Drain and cool slightly, then mash until smooth.
• Stir together warm water and sugar in bowl of mixer. Sprinkle yeast over mixture and let stand until foamy, about 5 minutes. (If mixture doesn't foam, start over with new yeast.)
• Add potato and 1/4 cup oil to yeast and beat with paddle attachment at medium speed until combined, about 2 minutes. Remove paddle attachment and attach dough hook, then beat in 4 cups flour and 1 tablespoon sea salt at medium-high speed until combined well, about 3 minutes. (Dough will be very soft and sticky.)
• Transfer to a well-floured surface and knead in remaining 1/4 cup flour with lightly floured hands until smooth and elastic, 8 to 10 minutes. (Dough will still be very soft and sticky.)
• Scrape dough into a lightly oiled large bowl and cover bowl with oiled plastic wrap. Let dough rise in a draft-free place at warm room temperature until doubled, 2 to 2 1/2 hours. Generously oil a 15- by 10- by 1-inch baking pan.
• Punch down dough (do not knead) and transfer to baking pan, then gently stretch to cover as much of bottom as possible (dough may not fit exactly).
• Cover dough with oiled plastic wrap and a kitchen towel and let rise in a draft-free place at warm room temperature until doubled, 1 to 1 1/2 hours.
• Preheat oven to 425°F with rack in lower third.
• Arrange tomatoes on focaccia (do not overlap), then sprinkle with oregano and remaining 1/4 teaspoon sea salt and drizzle with remaining 1/4 cup oil.
• Bake until center is firm, top is pale golden, and underside is golden (lift to check), 20 to 25 minutes.
• Loosen focaccia from pan with a spatula and slide onto a rack to cool slightly. Cut into pieces and serve warm or at room temperature.