Proof yeast in milk and sugar for 10 minutes; combine 2 cups flour and the salt; pour yeast mixture and 1 T olive oil into well in flour mixture; stir to combine, adding remaining 1/4 cup flour as needed; dough should remain soft and slightly sticky.
Scrape dough onto floured work surface and knead 5-10 minutes until smooth and elastic; place dough in an oiled bowl, cover with plastic wrap and put in a warm place to rise until doubled, about 1 hour.
Heat the remaining 1 T olive oil over moderate heat and cook the pancetta slowly until very crisp; drain on paper towels and reserve the drippings.
Boil the potatoes about 8 minutes or until tender; drain; in a bowl, pour the drippings over the warm potatoes; add the remaining ingredients and mix thoroughly.
Place a baking stone in the oven or oil a baking sheet; preheat oven to 375°; lightly punch dough down and knead 10 times; roll out to a 12" diameter circle and transfer to a paddle or the oiled baking sheet; oil the surface of the dough and let it rise 30 minutes.
Scatter the potato mixture over the dough and press in with the flat of your hand; without puncturing or tearing the dough, make evenly-spaced indentations over the dough's surface with your fingers.
Bake until the bread is crisp on the bottom and the potatoes are golden brown, about 25 minutes; cool on wire rack.