Flatbread with Fingerling Potatoes, Shitake Mushrooms, and Truffle Oil

In bowl of stand mixer fitted with paddle attachment, stir together water, yeast, and sugar until dissolved, about 5 seconds. Stir in milk powder until dissolved, about 5 seconds.

In large bowl, whisk together flour and salt.

Add to yeast mixture and mix on low speed until just combined, about 30 seconds. Switch to dough hook and mix on medium speed until dough is elastic but still sticky, about 10 minutes.

Using vegetable oil, lightly oil large bowl. Gently shape dough into ball and transfer to bowl. Turn over several times to coat lightly with oil, then cover with plastic wrap and let rise in warm place (75°F to 80°F, see Chef's Notes) until doubled in size, about 1 ½ hours.

Using vegetable oil, liberally oil heavy baking sheet. Using hands, lift dough from bowl and gently turn over several times to remove excess air. Shape into ball and transfer to prepared baking sheet. Cover with plastic wrap and let rise in warm place (75°F to 80°F, see Chef's Notes) 30 minutes.

Using fingertips, press and spread dough to edges of baking sheet. (If dough tears, mend hole by pressing surrounding dough together Cover with plastic wrap and let rise in warm place (75°F to 80°F, see Chef's Notes) until puffy, about 1 1/2 hours.

Preheat oven to 475°F.

In medium saucepan over moderately high heat, combine potatoes, 4 sprigs thyme, garlic, salt, and enough water to cover by 1 inch. Bring to boil, then reduce heat to moderately low and simmer, uncovered, until potatoes are easily pierced with fork, about 20 minutes. Immediately drain, discarding thyme sprigs and garlic. When cool enough to handle, slice potatoes into 1/4-inch-thick rounds and reserve. (Potatoes can be prepared ahead and refrigerated, covered, up to 24 hours.)

In medium sauté pan over moderately high heat, heat canola oil and butter until hot but not smoking.

Add mushrooms and sauté 1 minute.

Add shallots and sauté until light golden brown and soft, about 2 minutes. Stir in 1/2 teaspoon salt and 1/4 teaspoon pepper, then transfer to paper-towel-lined plate and reserve. (Mushrooms can be prepared ahead and refrigerated, covered, up to 24 hours.)

Arrange potato slices on flatbread, then brush with olive oil and sprinkle with thyme leaves.

Spread mushroom mixture on top, then drizzle with 2 tablespoons white truffle oil and sprinkle with 1 teaspoon salt and 1/2 teaspoon pepper.

Bake, rotating pan 180 degrees halfway through, until crust is light golden brown, 20 to 22 minutes.

While flatbread bakes, in small bowl, whisk together crème fraîche and remaining 2 tablespoons truffle oil.

Transfer flatbread to large cutting board and let cool about 5 minutes.

Drizzle with truffle oil–infused crème fraˆhe and sprinkle with chives. Using pizza wheel or very sharp knife, cut into slices and serve immediately.

•Dough rises best around 75°F to 80°F. If your house is on the cold side, you can set a container of very hot tap water near the rising dough and cover the dough and the hot water with a large plastic container or bowl—you will need to reheat the water every 30 to 40 minutes. Alternatively you can place the dough (and the small container of very hot water) in a microwave oven (not turned on) or a standard oven without a pilot light, but with the oven light turned on to provide gentle heat. •If you want to make this bread over a two-day period, once the dough has been kneaded, transfer it to a large oiled bowl, cover with plastic wrap and refrigerate overnight. (The dough can also be stored in a large re-sealable plastic bag, but leave a small end of the bag unsealed to allow gas to escape during fermentation.) The time in the refrigerator takes the place of the first rise. The next day, bring the dough to room temperature at least 1 hour before proceeding.